On the subject of relics and charlatanism, I think the Roman Catholic Church pretty much wrote the book on that. From the very interesting site The Vatican Billions, we can learn:
The more popular a shrine or a saint, the more abundant the collection of silver and gold coins.
The most fabulous was undoubtedly that promoted by the cult of the Blessed Peter, the Turnkey of Heaven. The cult demanded a journey to Rome, where Peter’s tomb lay. Peter had been crucified there, it was asserted with no more plausible data than a pious tradition, for the Bishops of Rome had no more evidence then than have the pontiffs of the twentieth century. The latter have attempted to substantiate it with doubtful archaeological finds.
The process, begun by Pope Pius XII (1939-58), was completed by Pope Paul VI.
In 1968 Paul declared officially that,
How the “identification” had been carried out, on a site where hundreds of thousands of bodies had been buried during many centuries, was not plausibly explained, in view also of the fact that there has never been any definite historical evidence to prove that Peter was ever in Rome. The Roman Bishops, however, cultivated the myth with undiminished eagerness.
This they did, not as mere upholders of a devout legend, but as the skillful promoters of a growing cult which had concrete and far-reaching objectives, since its magnification brought them immense authority, and with it money. For the belief that the tomb of Peter was in the Eternal City induced thousands of pilgrims, beginning with English and Scottish ones, to go to pray over the Apostle’s tomb; a source of tremendous revenue. Today we would call it by the more accurate and prosaic name of tourism.
The successors of Peter promoted pilgrimages to his “tomb” in Rome very early, although from the start they showed a special predilection for the richest and most powerful personages of the times - that is, for individuals who could give them costly presents, land and power. To quote only one typical case, Pope Leo tells us how the Emperor Valentinian III and his family regularly performed their devotions at the tomb of St. Peter, “such practice yielding a useful respect for the Apostle’s successors” to whom they offered costly presents and the tenure of lands. Pope Gregory, on the other hand (590-604), promised Queen Brunhilda remission of her sins.
Gregory went even further and sent the nobleman Dynamius a cross containing “fillings” from St. Peter’s chains, telling him to wear the cross at his throat,
The gift, of course, was not a free one. It cost money and gold. (3)
Not content with this, Gregory began to send out “the keys of St. Peter, wherein are found the precious filings and which by the same token also remit sins” - provided the recipients paid in cash or with costly presents. (4)
Once it became known that the relics of St. Peter, when combined with the spiritual power of his successors, could remit sins, it was natural that most of the Christians throughout Christendom longed to go to the tomb and thus partake of Peter’s and the pope’s spiritual treasures. The latter invariably involved earthly treasures of money, silver and gold, or deeds of real estate. And that is how the pilgrimage to Rome, called the Pardon of St. Peter, was initiated - curiously enough, mostly by Anglo-Saxons.
In addition to encouraging the belief that Peter’s tomb was in Rome and that his successors had “filings” from St. Peter’s chains, the popes encouraged the belief that by coming to the Eternal City the pilgrims could address the Blessed Peter in person. The Church, far from discouraging such dishonest humbuggery, gave her approval to it: witness for example the notable St. Gregory of Tours, who, in his De Gloria Martyrum, gave a detailed description of the ceremony that had to be performed in order to speak with the Prince of Apostles. (5)
The religious and even political results of this practice upon deeply ignorant nations like the Anglo-Saxons, and upon the Franks who imitated them, can be easily imagined. Secular rulers of the highest rank flocked to Rome. At the beginning of the seventh century, for instance, two Anglo-Saxon princes renounced their thrones and passed the remainder of their lives at the tomb of St. Peter. (6)
The well-calculated policy of this cult, once widely established, yielded increasingly valuable results for the popes, who were quick to turn the prestige thus gained into a powerful instrument by which to obtain the submission of men of low or high rank, both in the spiritual and in the secular fields. The accumulation of riches, which had not only begun to the a permanent feature of Roman Catholicism but had started to grow since the times of Constantine, when that Emperor had issued a law concerning the acquisition of land by the Church (A.D.321), by now had reached such a stage that it had become a kind of patrimonium, owned, controlled and administered by the Bishops of Rome.
The possession of property brought with it inevitable deterioration and indeed corruption of the clergy and therefore of the Church herself, since the former, seeing the latter’s eagerness for the things of this world, followed her example. The clergy, for instance, began to ask for money in exchange for their work or made money out of church goods.
It is no secret that during the time of Constantine, pagan temples were either closed, transformed into Christian shrines or demolished. Their properties were summarily added to the Church’s patrimony. The wealth of sundry religions was mercilessly expropriated, their clergy dismissed or persecuted, when not civilly or even physically obliterated. This transfer of political might made an easy transition into acquisitional power, the Roman Catholic Church set out in earnest to promote a policy of swift appropriation of real estate, of highly remunerative governmental posts, and even of speculative monetary and commercial enterprises. (see above link)
It's easy for some modern-day Catholics to condemn the "Protestants" for loss of their "property" of important relics, but let's not forget that it was Roman Catholicism that started that ball rolling.
Dionysius of Corinth mentions the burial place of Peter as Rome when he wrote to the Church of Rome in the time of the Pope Soter (died 174), thanking the Romans for their financial help. "You have thus by such an admonition bound together the planting of Peter and of Paul at Rome and Corinth. For both of them planted and likewise taught us in our Corinth. And they taught together in like manner in Italy, and suffered martyrdom at the same time."[14]Fourth century mosaic of St. Peter, Catacombs of St. Thecla Catholic tradition holds that the bereaved Christians followed their usual custom in burying him as near as possible to the scene of his suffering. According to Catholic lore, he was laid in ground that belonged to Christian proprietors, by the side of a well-known road leading out of the city, the Via Cornelia (site of a known pagan and Christian cemetery) on the hill called Vaticanus. The actual tomb was an underground vault, approached from the road by a descending staircase, and the body reposed in a sarcophagus of stone in the center of this vault.
The Book of Popes mentions that Pope Anacletus built a "sepulchral monument" over the underground tomb of St. Peter shortly after his death.[15] This was a small chamber or oratory over the tomb, where three or four persons could kneel and pray over the grave. The pagan Roman Emperor, Julian the Apostate, mentions in 363 A.D. in his work Three Books Against the Galileans that the tomb of St. Peter was a place of worship, albeit secretly.[16]
There is evidence of the existence of the tomb (trophoea, i.e., trophies, as signs or memorials of victory) at the beginning of the 2nd century, in the words of the presbyter Caius refuting the Montanist traditions of a certain Proclus: "But I can show the trophies of the Apostles. For if you will go to the Vatican, or to the Ostian way, you will find the trophies of those who laid the foundations of this church."[14]
These tombs were the objects of pilgrimage during the ages of persecution, and it will be found recorded in certain Acts of the Martyrs that they were seized while praying at the tombs of the Apostles.[17]
During the reign of the Roman Emperor Valerian, Christian persecution was particularly severe. The remains of the dead, and particularly the Christian dead, had lost their usual protections under Roman law. The remains of Peter and Paul may have been removed temporarily from their original tombs in order to preserve them from desecration by the Romans. They may have been removed secretly by night and hidden in the Catacombs of S. Sebastiano in 258 AD, being returned to their original tombs in 260 when Valerian's reign ended.[17]
Wikipedia (Links work at the source)
Generally, I would say, relics in Italy and south of France, -- regions not infected by Islam, Protestantism, or Communism -- tend to be most often authentic.
The Church has existed for 2,000 years on voluntary donations. Yes, they amount to real money.