How deposits works is the ultimate Kobayashi Maru.
Deposits, in my mind, should be the basis of a contract that works to both the seller and the buyers advantage.
Many years ago I sold a 1994 Defender 90 with a rare aluminum hardtop. Flawless.
I priced it well and received an offer and a deposit within a day, which I accepted. The market was nuts on these things then and later that day I received a number of other offers above and way above my asking price.
One guy got pissed at me because he couldn't believe I wouldn't take his higher offer.
The guy who bought the D90 was from San Francisco. Great guy.
So query the guy when he asks for his deposit back what he would have done had you gotten a higher, less cumbersome offer after you accepted his deposit and decided to take it, leaving HIM disappointed.
Keep a $100, you know, for the effort
Good ad, btw.