It is not clear to me whether the topic arises, to the Talmud, or whether there was any possibility in their day of such, but lately, there may likewise be a proportion of increase in a coin's value above and beyond the value from the inscription. Could this be prohibitive as well, to incur penalty of mechac batul, for instance, if the coin was intentionally too valuable?
H David Levine, Roanoke, VA USA
Shalom R' Levine,
Correct me, but if I understood you accurately, you are asking this: A customer wants to buy an item for a dollar and accidentally paid for it with, let's say, a rare collectors edition silver dollar. So, really, the precious coin was worth much more than the one dollar item. So can the buyer claim the deal is invalid and get his coin back? I looked in Shulchan Aruch Choshen Mishpat 227:15-16, which discusses price fraud as it applies to movable objects including coins. It does seem clear to me that we assess the value of the item, in your case, the very valuable coin, simply based on the price it would sell for in the marketplace. I would like to keep my eyes open to see if any other sources speak directly about your specific issue, and if I find greater insight, bl"n I'll be happy to try and share it with you.
Warmest regards,
Yishai Rasowsky