"Entrepreneurship is like one of those carnival games where you throw darts or something.
Middle class kids can afford one throw. Most miss. A few hit the target and get a small prize. A very few hit the center bullseye and get a bigger prize. Rags to riches! The American Dream lives on.
Rich kids can afford many throws. If they want to, they can try over and over and over again until they hit something and feel good about themselves. Some keep going until they hit the center bullseye, then they give speeches or write blog posts about "meritocracy" and the salutary effects of hard work.
Poor kids aren't visiting the carnival. They're the ones working it."
But then the seller is missing out on those $50, which they can't spend anywhere else. From an macroeconomic perspective, the effect is zero. Like advertising, it only serves to allocate resources, not to create value. What's more, it's mainly large companies that benefit from something like this. Firstly, because of scale effects, and secondly, because they can sustain price dumping for longer than smaller companies.
The same applies to deals. You only benefit from them because someone else is disadvantaged. Unless, of course, you assume that companies have something to give away out of kindness. And, of course, you yourself have been someone who has given someone else an advantage at your own disadvantage. You paid more so that someone else could pay less. The macroeconomic effect was zero because no value was created.