Local/regional chains seem to stay more reasonable, but honestly, local restaurants in my area are almost cheaper than fast food. A typical combo meal seems to run around $10-15, and you can find lunch specials and weekly specials for $8-12.
The food is way better as well.
I could go to Arby's for a combo (roast beef sandwich, soda, and fries) and spend around $14. Or I can go to the sushi place half a mile away and pay $11 for their made-to-order bento box: teriyaki salmon filet, small salad, 3 gyoza, 4-piece Cali roll, and tasty rice. I haven't been to Arby's in years.
The Costco Hot Dog is a 1/4lb hot dog sold at the international warehouse club Costco's food courts. It is notable for its price, which has remained steady at $1.50 in a combo deal including a soda at United States locations since its introduction in 1984. That price has become increasingly low relative to inflation and spawned a cult following
From the wiki
A lot of America centric answers, so I'll give a more global one: Ikea or any comparable store which uses cheap meal deals as a loss leader to get you to shop in their store. AFAIK the costco hot dog is the most famous US example.
This being said: eat/cook at home. Rice based meals can be made for as little as a dollar per serving, if you buy in bulk. (Get a cheap rice cooker, it can do more than cook rice, save on energy costs, and takes out most of the hassle.) Potato based meals are also very cheap. Baked potato with a bit of butter contains much of the nutrients you need to survive in the short to medium term.
For the level of "quality" they delivered, they have always been too expensive.
Chipotle, especially for the amount and quality of ingredients. I used to splurge occasionally and get their quac (edit : okay that's not... quite the right spelling for "guac" there:-D) for a dollar... I haven't done that in years since it went up to like $3. Be careful of salt content.
Chain restaurants often times will be more expensive than small, hole in the wall places. Part of that is the price of rent that gets passed onto the consumer. If you have the option, I'd say try to find a taco truck, food window (no seating area), or grab and go food from a grocery store.
If you're in Seattle, Dicks Drive In is still relatively cheap compared to McDonalds.
A lot of folks are suggesting fast food apps help you continue getting cheaper prices on their low quality meals. But not much mention that you are selling your data to continue receiving those meals at those lower rates.
Waffle House if you don't mind dining in. They're everywhere. They're always open. You'll almost always leave entertained by the sheer mixture of colorful personalities.
Taco Bell has $6 boxes in the app. BK has monthly coupons in the newspaper for the $18 family meal pack that is enough for my family of 4.
Where I'm at, pretty much everything else starts at $12 a person, or $16+ at sit down/local places.
I live in a semi rural dying city. Our cheapest options are just going to local joints. It may not be as quick and you may have to speak to someone, but I just recently spent$60 for mid ass Mexican for two and I would have much rather picked it up. Now I admit I was being lazy and just got paid.
For McDonald's you have to use the app to get any kind of deal.
In Australia KFC is more economical than McDonald's now - especially is you use some of the permanent deals in the app.
We have all but stopped drive thru when out for a concert or other events. What we do now is pack some home made sandwiches with some chips, etc for the drive home.
I still do mcd sometimes when working but I only order off the deals or redeeming points for something. I never pay full price.
Panda Express! Why does McDonald's even exist??!
Costco hotdogs
Where I live it's the chicken places. I can get a meal and a drink from church's or kfc for under a tenner.
PTerrys in Austin is bangin... Best fast food fries. You can get a double cheeseburger meal for $8.
Food trucks tend to run cheaper as they cut down a lot of expenses in their operation compared to restaurants with dining areas, staff, drive thrus, etc.
On top of that, I have found a few random local places with rather decent prices. A pub in town, a chinese restaurant across town, and a diner. They took a while to find though and not all their items are cheap. I am also finding places are incorporating delivery apps into their operations to avoid paying out as much too through middlemen.
I don't go there but when I'd drop in to use a bathroom while travelling I always found it shockingly expensive. I'd rather go to the local hole in the wall dumpling joint and get a plate full of real homemade and inexpensive food any day.
