Promo loads of all the major manufacturers have less hardness to the shot, thus producing less reliable patterns. Premium loads like Winchester AA, Remington STS and Federal Gold Medal have high antimony shot having maximum hardness. There is a reason for premium priced ammo.
You are right, cheap loads are not the reason for misses at pasture Trap or the 16 yard line. It can make a difference to high end shooters shooting Handicap Trap.
The cheapest of the Promo loads are often deficient in quality control these days, with bobbled crimps and damaged metal base - Winchester Universal being the worst offender, in my experience.
Some guns have trouble extracting the steel head promo loads from some manufacturers, largely due to mismatch of chamber tolerances vs. cartridge head diameter.
Having said that, I have never had a failure to extract, with a very wide variety of shotguns and cheap ammunition.
You have to shop the sales to get the best price on shotshells, or have access to a shooting club's bulk buy.
Winchester AA come on sale every year in early Summer, and offers a $2 a box mail-in rebate, if you decide to buy top quality ammunition.
Otherwise, the best deal on economy ammunition that I have seen recently was Federal Top Gun at Cabelas on Canada Day, $65 per flat. If you had a $20 off coupon, when spending $150, you could get 2 flats plus a couple of boxes for $6.70 a box, two taxes included, here in Saskatoon. I cannot load shotgun shells for that low a price with the cost of components these days, particularly the cost of shot.
