Several decades ago* The Wizard Of Id had a strip which went roughly like this: Apple seller has a sign : “Apples 25 cents, 3 for a dollar.”
A customer has an expression of glee, and buys FOUR for a dollar, then goes off happily thinking he’s outsmarted the seller.
The seller winks at the readers, and says “nobody ever bought more than one, until I put up that sign”
So, OP, you bought 20 McNuggets cheaper than the menu lists it. But would you have bought those 20 at all, if you didn’t think you were outsmarting them? Without that sign, maybe you’d have only bought 3x4 piece. Perhaps their pricing scheme persuaded you to buy 20, when you would otherwise have bought 12.
Probably 4 piece meals are eaten mostly by kids (and dopers who do the math). A lot of kids don’t want sauce so they don’t give it out and waste it unless asked.
At my store we were trying to sell through some snack crackers by putting them on sale for 99 cents. The sale wasn’t working so I asked my boss if I could mark them down lower. He told me not to and that instead we should put up a sign that said 10 for $10. I told him he was nuts but did it anyway. The next day when I came in he showed me the figures. We whent from selling ones and twos to selling them in increments of ten.
OTOH, if something is on sale without a standard per-package price, just an X for $Y price, AND the price is cheaper than I could normally get, I usually do get the listed X amount, because you never can tell if there will be a higher per-package charge. Used to be you rarely saw a separate higher charge, but it happens quite a bit these days.
