I don't pay for flints at all anymore. Have a couple hundred pounds of flint that cost me nothing but the exercise to collect it, and I make my own. I'm certainly not Tom Fuller, and they aren't always pretty (ok, they’re almost never pretty, actually), but they work. Get usually between 10 and 30 shots from those that work. Maybe 8 out of 10 work, some just won’t spark, but since they're free that's not a problem.
Just takes a good supply of flint and a lot of practice to be able to knap your own. Lots of waste at first, but like most things you get better with lots of practice.
If you are going to have to buy raw flint, it would be cheaper to just buy the finished gunflints, otherwise you’ll end up with a lot of expensive flint chards and 2 or 3 usable gunflints when you start making your own. :wink: