Shotguns are not like rifles in that the brand of ammunition will alter the point of impact to a great degree. It may change some, but not enough to cause a complete miss at the range that you will be shooting. Also, as you know, the pattern will get larger at increasing range. Having said that, I think you could use the less expensive shells to dial in your pattern's center of impact, then switch to your better patterning shell for hunting with confidence. Just hold a tight bead on the waddles on shots inside of 20 yards until you know exactly where your center is going with your hunting shells.

good luck!