"A woman's desire for a man is inversely proportional the the size of penis/wallet."
Based on your sentence structure, you're pitting desire against penis size and/or wallet size, not penis size against wallet size. So her desire goes up as penis size and/or wallet size goes up. That would make them directly proportional. You said inversely proportional, which means her desire would go up as his penis size and/or wallet size went down, and vice versa.
I get what you meant to say, but this is what you did say. Have a nice day.
