'Top Dollar'
This is one that, I feel certain, has strayed far from its origin.
I have only a guess that relates to the practice of keeping a stack of folded bills in a money clip.
It was customary to put the larger (better) bills on the inside so as not to reveal your true wealth. Most transactions required simply 'peeling' a bill(s) off the folded stack.
If your purchase was more substantial you would need to:
a. unfold the wad
b. remove some of the bills on the top of the stack

The TOP DOLLARS, eh?

What thinkest thee?

"I am certain there is too much certainty in the world" -Michael Crichton