First recommendation, Try reloading one of the versions from itch, or from itch app, That's definitely a first I've heard that, unless you have like 2200 charisma or something... even then I don't think Tin is expensive enough to zero out.
Also I would try to recommend starting a new save, as I feel like maybe it almost sounds like you're using an old save where the Currency was a different type.
Previously the current was just " a currency" and you'd have hundreds of millions of "currency"
Now its Copper, Silver, Gold, etc coins, and I know Slipcor made a save fixer related to money issues from one specific version to one specific update, but if you save and reload, before using that, you're pretty boneroned I think.
I didn't have either of those cases, so I don't know how "being boneroned" looks like, but what you describe does sound like what I could imagine would come from that.
as 1000 copper, is 1 silver
and hitting more than 1000 copper, Turns that into silver, and any extra beyond, turns copper, until 1000 silver, which turns to gold.
Also keep in mind that alloy bronze, is a wonderful thing.
Bronze (1 tin 1 copper) creates 2 bronze, and each bronze is worth 650, instead of tins 500 and coppers 10
Brass is 750
Steel is "enough" more than Iron to be noticeable, but then again, you get 2 steel for 1 iron (and 1 carbon)