I'll have to go back and check my old emails- we used to buy USPSA (and sometimes IDPA) cardboard targets from somewhere... I seem to remember that they were almost the same price or cheaper from Midway.
We were buying 500 at the time from some company for the old gun club. That was a lot of boxes at one time. They usually got shipped to someone's house and we unloaded them into the container (i.e. storage unit) that was at the club. I think it worked out to about a dollar per target.