ORIGINAL: barefoot
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!
My experience is different.
In working up my Mossberg 835, 24" barrel, Star Dot .676 choke, and I found significant differences in the POI for different loads. I started with cheaper winchester shells to do a rough sight-in then moved to the Nitros. Had to make a sight adjustment but it wasn't drastic and either load would have likely taken a bird. No big deal. I was working the gun up for the 3.5" Nitro Triplex 2.25oz load so it was fairly easy to get it "perfect" with 3 or 4 additional shots.
I had a couple of the "older" Hevishot 3.5", 1 3/4 oz loads and was interested in seeing wherethey would hit relative to my primary hunting load, the Nitro Triplex, because I wanted to use them as back-up shots (those Nitros are $$$ you know). To my amazement the center of the pattern was about 10" high and left. Enough to miss. I'm glad I did this because I learned that those were not suitable for backups in my setup
Makes sense once you think about it because the velocity for that Hevi-13 1 3/4 oz charge is significantly different from the 2.25 oz load in the Nitro. That would explain the fact that it was shooting high relative to the Nitro. I can't explain why it went left, but it did.
Another friend of mine changed chokes ona whim(went from a Rino to a Pure Gold) without shooting the gun to confirm POI. Next day he missed the first bird clean then crippled the next one but got him anyway (thankfully). Upon returning home he found out the Pure Gold shot way left and high relative to the Rhino with the same load.
Gotta check that POI if you really want to be sure.
Mouthcaller