In regular training shoes I can barely run a mile without getting some pretty bad pains in the side of my knee. With good cushioned running shoes I can easily do 10-12 miles pain free.

I'm assuming it's a form thing, and that the running shoes just somehow naturally give me a better form, so I could maybe fix by learning how to run in normal non-running shoes, but I'm lazy and would rather just pay a few hundred every few months.