Gotta love modern cars.
Yeah, you can drive on them despite them being flat for a certain speed and limit. The walls of the tyre are strengthened.
The tyres I had aren't run flats, but they have a goo inside the tyre that 'self heals' should there be a small puncture. The puncture I had was a screw so the goo wasn't able to fill in the hole. Great tyre nonetheless. The expense is probably due to having to run SUV specific tyres too.