Well, you asked for the average range session. I do not shoot asmuch as I used to. I used to shoot a lot more at each session because I was a range officer at that time - up until September or October 2003. When I got to the range then, I probably shot at least 300 to 400 rounds per session, which at its height was going 3 sessions a week for up to seven weeks. If I was not instructing in the classroom, then after the range was set up, I had some time to kill before the shooters came out.
Now a days my average range session is harder to figure. I still shoot quarterly qualifications where I shoot about 150 rounds (which soon will increase to about 240 when I am reissued an MP5). I guess I have shot as few as 10 rounds while I watch my son shoot the rest of the session. He is not permitted by law to shoot on his own because he is 15, so I have to watch over/instruct him yet; he could probably instruct some instructors on range safety. Other times I let him shoot a while, then I take over with maybe nine fully loaded 15 round 9mm mags, shoot quickly, then relaod as he shoots again. Then finish up the second round of nine 9mm mags. That would be 270 rounds, plus some 22LR or maybe larger bore ammo like 35 Remington.
I guess all in all over all the years I have been shooting I have to figure my average as between 300 to 500. My average as of late is between 100-300.
The cost of ammunition only restricts me when I am shooting something like .35 Remington. At about $14 per box of 20, it is a bit expensive. When I shoot military surplus rifles the cost of ammo is not a restrictive factor because the ammo is dirt cheap. When I shoot 9mm ammo cost is not a factor because I can get all they will give me, which is almost all I could want, at work. Not a bad fringe benefit. One limiting factor is Range cost though. It is pretty expensive at my nearest range. The other range I go to is a bit of a hassle time wise (takes a while to get there). It is also a hassle range officer wise. They yell at you if you stand to shoot as you are limited to sitting at a bench but, this rule is not (or was not) posted in plain view; this was for rifle shooting. They use the cease fire command but do not expect shooters to cease fire when they say it but only to be ready to cease fire; then tell you to 'stop firing' to actually achieve a cease fire! It got my ears once because of that. Kind of really weird stuff as compared to any other range on which i have fired but, when I had asked at the check in counter if there were any rules particular to this range they in essence said 'no everything is normal'. Well the ranges are what limit my personal fun time shooting more than anything. Still I try to shoot at least monthly, more often when I can. I prefer to shoot at least weekly and then would prefer to shoot at least 300 to 400 rounds.
All the best,
GlennB