“Why at home not in a bank vault?”
Why not sell them and help the poor in Mexico?
Judas Iscariot asked the same question once.
Pectoral crosses and rings are official signs of sacred office, and were paid for via the donations of people who wanted the money spent for ecclesiatical furninshings and vestments. So diverting the money to a different use and allowing the consecrated crosses and insignia of the church to pass over into the hands of, e.g., private collectors, would seem to be a violation of fiduciary trust.
It would be better to just raise money for the direct purpose of helping the poor in Mexico and elsewhere. Which the churches do on a regular basis, for instance in collections which go to Caritas, CRS, and Peter's Pence.
The Peter’s Pence Collection raises nearly $190 million annually to provide emergency assistance to those who are suffering as a result of war and natural disaster.
The national collection date for the Peter’s Pence Collection was just last weekend, June 28th and 29th, 2008 (Feast of Ss Peter and Paul.) If you're interested in helping the poor, you might consider this helpful link.