While it is possible these coins are the rare ones, I know I have seen coins like this in the local coin shop and they are probably far from "priceless". I bought several of them for very cheap. (not 20,000, however)
They are mostly copper or some other soft metal stamped with the image of the "leader of the moment" for whatever part of the empire they were created in.
I guess there were so many created for circulation, they don't bring much value to collectors.
We have some old Roman coins my brother bought from a coin dealer on the Internet.
They were not very expensive, I think he got 30 assorted coins for around $64.00.
What is cool about them is that even though they are not precious metal they actually are a part of history that you can own.
A few of the coins we have are from the time of Constantine. They have his inscription on one side and Romulus and Remus nursing from a wolf on the other.
One of the reasons that Roman coins are found buried like they were in this article is that Roman soldiers sometimes pooled there money together before a battle and buried it. Whoever was left alive after the battle could split the money.
Many times no one lived through the battle so the money stayed hid.