no americans are dumb

Your prices seem very reasonable, even when converted to USD. Most payment systems do the conversion automatically, so that shouldn't be an issue. Maybe try an experiment and, rather than relying on the conversion, just offer two different pricings? For example:

ART TYPE #1 - GBP 3/USD 5
ART TYPE #2 - GPB 6.25/USD 10

You have the choice to update it occasionally or just let it average out. Might work until such time as you're absolutely swimming in commissions. :)

I know that my prices are reasonable, but I can understand if someone sees the abbreviation "GBP" and goes "Oh snap, currencies".

I think I might translate them to USD for a while when I next have an ad up, and see if that makes any difference. It'd be really neat if FA had a built-in currency converter, but I doubt that'll happen any time soon.

Yeh, I'm probably unusual in that currency conversion doesn't bother me.

that's really not that odd, I actually find it strange when people make a fuss about having to convert currency

As do I, but it seems to make a difference somehow. It's peculiar.

Not in the commission info tab, no.

This is true, although knowing people, I doubt they'll read the info.