Chekov smiles and goes with the illusion that he actually understands how this money thing works. He might joke about a lack of money, but, being from a world where currency (and gambling for money, incidentally) is extinct makes it difficult to care about the accumulation of monetary wealth. With the various jobs he has in the City, Chekov has more money than he knows what to do with. It's fortunate that Lucy helps him spend it.

Speaking of Lucy... "I never knew anyone like her at home. I'm cursed; very few women think of me as anything but a sibling who needs to be fussed over, and even fewer are half so beautiful and funny as Lucy is."