I can't tell if you're implying that Wendy's was going to offer different prices to different customers "on the fly", but that wasn't the case.

It was store-wide with updated prices shown clearly. Yes it could change on a daily basis, but you would also expect it to be roughly predictable because the whole point is to get more people to come in when it's cheaper.

Saying that Wendy's is "pinching pennies" doesn't make any sense.

So... you just apparate at Wendy's instantly without cost when you decide to go? Most of us aren't so lucky. We need to travel there, which takes time and resources. Sometimes we decide to go through the drive-through and there are 5 cars in front of us and soon 3 more behind us blocking us in. When prices are 20% higher than you expected when you finally get to order, do you leave and waste all that time? Do you pay 20% extra, giving them money for nothing? Economically, both of those options are losses.

(Yes, I understand that Wendy's claimed it was only ever going to be used for discounts. But frankly, I don't believe them. The temptation to increase prices is just too powerful to ignore for a profit-maximizing MBA.)