Howdy Aaron.
FWIW, I average $25 - $40 (U.S.) per hour per person on my jazz gigs. Sometimes meals and/or drinks are included, sometimes not. If so, don't abuse the perks.
Private stuff usually gets 1.5x to 2x more. A special date like like New Years Eve sometimes garners 4 or 5 times more.
I've read Ed Friedland's
A Working Bassist's Toolkit, where he addresses the same question about money. From what I remember (and it's been a while, so I could be wrong), I don't think these #'s for "casual" gigs are too far out in left field. [ Or maybe it was an article Ed wrote for BP magazine. I can check the book later if you're interested. ]
There's also usually like a $100 per person minimum for those really short gigs (1 or 2 hours).
I think you have to be sensitive to what other groups that play a similar style are charging. It will vary from one city / town to the next. Can't set the bar too high, 'cuz you'll never get the gigs. Can't set the bar too low, 'cuz you'll do all the other musicians in your area a great disservice. The club owners will start to say "Well so an so's band plays for less ...". Don't piss off the other working musicians in your area by trying to undercut the going rate.
You also have to size up the clientele for those private gigs on the spot. If they look and act like they can afford big bucks, go for it. You'll know the type. Full of themselves.
On the other hand, don't lowball people. You might get a few more gigs, but in the end you've backed yourself into an ugly corner. Try to go for a fair & reasonable price. And don't be afraid to use that exact verbiage, "fair & reasonable." I've used it when negotiating a price for selling and buying a house for example. If you lose a few gigs because some folks thought the # was too high, I say "So what?" It has happened to me, but I still get plenty of other calls, and I still get treated fairly IMO.
All this comes with a huge FWIW, YMMV, etc., etc. Others might scoff, or drool. I dunno. I am just trying to be candid and share the reality of my situation. I've been earning money part time playing music since 1979. Ironically, wages for musicians for these types of casual gigs in my area haven't really changed much since then.
