I don't want to have to think about how many miles my tyre has done after 1000!!! Buy cheap, buy twice. There might be exceptions, there are always exceptions, but the majority of the time this is true.
I've spent over £100 per piece of rubber, but they'll last years and several thousand miles. I'd rather skimp on a night out than the part of a car that sticks you to the road. Same with brakes tbh.