30 pieces of silver, is the price paid for Jesus to Judas. They said "coins" but not if they are golden, silver or bronze/copper.
Denarius and Sestertius are the most famous Roman currencies I think. But here by "coins", I think they mean "asses" (as).
To understand the value of the currency, the denarius had the value of one day of work for a manual worker (they worked maybe around 6 hours a day, as they worked from the sunrise to midday)
I've found a webpage claiming that the price of the wine was: "1, 2, 3, or 4 asses per sextarius or pint; by comparison, a loaf of bread cost 2 asses".
So 30 asses, is far too expensive. Should be divided by 10 (but we don't know the bought quantity).