Russ,
The problem you're encountering isn't an error in math, it's an error in
understanding. You're misunderstanding is common becayse Ebay words thier
rules rather crappily.
You are charged 5% of all sales up to $25
PLUS an additional 2.5% for $25 to $1000.
So using the printer that sold for $41, you get charged 5% for the first
$25 (1.25) then 2.5% for the additional $16 (.40) for a total of $1.65.
I know, it's a weird system :)
Tony