I totally agree with you, but there are people who refuse to see it that way. If there was an ice cream cart at the bottom of the Grand Canyon selling a scoop of ice cream for $10, some people would be outraged. Never mind that it's a remote location, it's very difficult to supply ice cream there, it's incredibly convenient to be able to buy ice cream there, etc.

For Blockbuster selling snacks, no one is under any pressure to buy snacks there. If you're really pressed for time or don't want to drive to another store for snacks, then maybe the ludicrously high price is worth it. If it's not worth it to you at that moment, then don't buy there.

It's only bad if there's a monopoly or some other form of coercion involved, which is clearly not the case for Blockbuster selling snacks. And yet, to some people, it proves that Blockbuster is the devil...

Convenience stores also generally have a markup versus grocery stores. That they had a markup above that was always a bit questionable. My recollection is that over time they switched to some more niche candies, things you couldn't necessarily find down the street and so the apples-to-oranges problem gave them a bit of an excuse.