What are some ways exchanges make money, other than upfront fees?

Hi!

I'm trying to figure out all the ways exchanges make money. I'm mainly focused on the sneaky methods that aren't clearly disclosed, but I'll take any verifiable cost. Here're the methods I know of so far, based on experience and reading a couple public board of directors call transcripts:

1. Normal exchange fees. You buy X we charge 0.2% on top.
2. Spread capture. The market price is $30, but we buy for $29, and sell for $31 - making an extra dollar in either transaction.
3. Gas fees. Set a flat fee of $5. Usually they make a buck or two, occasionally they lose during high traffic
4. Pulling out fee. To move crypto from exchange account to private wallet costs x% of total moved. I imagine this is also a good time to capture some spread, but I don't know for sure.

Anybody have insights? Admittedly, I haven't used an exchange since the glory days of FTX.