Q: How much did that security system cost?
A: We paid top dollar for it.
Q: Will it be sunny tomorrow?
A: You can bet your bottom dollar.
In the above two examples, and in general, “top dollar” and “bottom dollar” mean the same thing: lots of money. Why? Is there any similar phrase that is used to mean the opposite (not much money)?
No, they don’t. “Top dollar” means the highest price, or most expensive". “Bottom dollar” means your last dollar; betting your bottom dollar means you’re betting on such a sure thing that you’re willing to risk your last dollar on it.
What Q.E.D. said.
(I always get to these late.)
Ditto!
“Bottom dollar” was used to mean your “last” one from the middle of the 1800’s.
“Top dollar” is only from the mid-20th Century as far as I can find.