Let's ask this question in a different way:
If you are a new "investor" would you pay for a new franchise to Carl's Jr selling $2 famous star, $12 for a family of customers (3), with 5 employees, and full AC? I personally wouldn't.
What this means is, this is probably no longer sustainable and people who opened this years ago just didn't stop it because of sunk cost.
Newer fast / fast casual food are like Pinera Bread / Chipotle that cost $10 per customer on some cheap food that has less cost per customer than Carl's Jr. Look at Chipotle's burrito, probably about the same amount of meat in famous star, way more rice, some extra sauce and same amount of wheat flour in the tortila than the bun in famous star, and now instead of $2 they are selling for about $8-10. They have about 5 people in the store and their customers are probably 4x.
Panera bread doesn't even need as many people, sell bagel in the morning and sandwiches at lunch and dinner, chips are prepack instead of fresh fried fries, and their set of sandwich sell for like $8-10 instead of $6-8 with way lower cost.
The thing about profit is, you have to aim for the mid-high end instead of the bottom of the market where there's no money to be made.