What would you charge in this situation?

You've just picked up some multi-track recording gear. Not top of the line stuff but, semi-pro and good enough to get the job done. And, you wanna try it out to get used to what it can do so, you figure you'll take it out (or, have them come to you) and record local bands that are kinda just getting started and, on one hand, you're learning your gear and they'll end up with at least a fairly to pretty good demo to shop around.
How much would you charge them? You don't wanna scare them away by over-charging but you also wanna get SOMETHING worth while out of the deal.

What would you charge in this situation?
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