I went the other night to get comfortable with my P30. Took about 500 rounds and several guns. Brought plenty extra in case someone else that was in our party wanted to try one of mine. My wife ended up shooting 200 rounds between everything including my HK. I ended up shooting 300 in just my HK.
I must say I will not make that mistake again though. The last box or two was a waste. My hands were getting tired from gripping and I think I was going cross-eyed. After the first magazine my groups tightened up nicely. The last box was way worse than when I started.
We all try to get together atleast once a month and shoot. But like you said, I will not bring "extra" anymore.
Also I sold a USPc .357 with a .40 barrel also for $650 about 6 months ago. We were both happy with the exchange. Not sure what it was actually worth. But like has been said before, anything is worth what someone else is willing to pay for it.