That's a lot for just hamburgers. It's just hamburger meat.
I can go to Chipotle or Qdoba and get a steak/hicken burrito and a steak taco, and a drink for $12.
I can go to Boston Market and get a half chicken, 2 sides and a drink for $12.
Also, just because they been around a long time doesn't mean that they have staying power as a national franchise. Krispy Kreme has been around a long time but couldn't become more than just a novelty. Boston Market tried to expand and that didn't work out. There are plenty of examples of businesses that were successful for a long time, then branched out, over expanded, and eventually struggled to stay in business.