Yup, that's pretty par for the course at most places that sell by the slice. Dollar slice places now mostly charge $1.25-$1.50 for a plain cheese slice.
Seems ridiculously cheap to me. here in Phoenix, there are 2 restaurants near me that do by the slice, both around $5. Most restaurants don’t offer it.
I have only spent a month or so in NYC working a decade back, and at the time every thing was more expensive than home except pizza. I think every region probably has its cheap food for the working class. Here it’s tacos, there it was cheap slices.
How big are the slices near you? Im assuming large-ish like a NYC slice, where 6 slices will make the pie. If you are paying $5.00 for a slice of cheese pizza in Phoenix, that means a whole cheese pizza would cost $30 USD? That is insanity. Granted I think it would be cheaper if you bought a whole pie, but for dough, cheese and sauce that is still a very healthy profit.
I agree every region has its own good cheap food. Interesting stuff.