From Eamonn Butler's book, The Best Book on the Market:

People trade what they have plenty of, for what they want instead.
I could develop this train of thought, but it would probably be obvious. Let me notice, at the very least,
that bar-host Dee has plenty of sexual energy, which he wants to trade for things he wants instead (food, money, clothing, education and (even) perhaps a man who really cares about him.)

Things get a bit more interesting when you realize that both parties actually need one another.

Stay tuned for Henry's Law #2! :-)