Just a FYI, it's common practice for these pet stores to order all their fish in, on Wednesday or Thursday and sell them on the weekend. This is definitely a time where you want to quarantine your fish you bring home, and really scrutinize over the health of the fish you're going to buy. They can get away with this, because they know if you don't buy it, the 40 people in line behind them will.
I've even seen fish unbagged and sold in the same hour at these sales. I won't name the stores, but it is a common practice between them. And as a disclaimer, I've never been to Denny's on an anniversary sale. The times I have been there though, I'd say 50% off might just make some of their fish market price
I've seen $75 royal plecos etc there.
Their niche is to have high priced fish that sell slowly, which leads to healthier fish. A fish that sits for 6 months, and then is sold is much more likely to be healthy, but comes at a higher price.
Be an informed buyer. 50% off of a dead or dieing fish is 50% too much.