What chain can you get a pizza for $8.50? Only one I can think of is Little Caesars (which I personally adore, but I am a living trash can). Actual question, pizza is hilarious inflated price wise used to be a cheap treat.
Maybe you should learn to make pizza at home. Detroit style pizza is relatively easy to make if you know how to produce bread. Thin crust can be done, it's just a little more effort.
Where I am I can consistently get bogos that make the premium frozen pizza brands about $5 per pizza. There are also cheaper store brands that are $3-4. Definitely cheaper than dominos/Papa John's. Especially since they've raised there prices considerably in recent years as well as stopped offering the kinds of deep discount specials and deals they used to offer.
The most basic of basic vegan pizzas I can get at Lidl here costs like less than 2€ per pizza. Topped with some tomatoes, maybe some additional cheese, vegan salami or something and I'm cookin. The fancy vegan pizzas cost like 3€