LOL mike, 'in stone' is an expression meaning it something is definite.

Set in stone means unchangeable or not changing.

Supply and demand changes prices accordingly. A price set in stone is a price that is established and will not change under any circumstances.

Good day to you sir

I'm sorry, but I didn't realize the communists have migrated to Minetown. Prices set in stone destroy the theory of a capitalist economy. There is no more possibility of merchanting, trading, profiteering, et cetera. I have no plans of honoring any conversion rates in the borders of Espero.

you know what i say? Bargain. Try to find a price you can both deal with.

If you have something that the other person wants you make a fair trade, how hard is that. Wth do you need conversion rates for?