Cerakoting is only expensive if you pay a shop to do it. A 4 ounce vial of Cerakote (at least 100 different colors to choose from) is around $35, and will do all the parts on 3 rifles if you don't get carried away.
Anybody with a small pancake air compressor, a$30 touch up spray gun, and an oven in their kitchen can do it.
You'll need to sandblast the parts as well before spraying. I bought a $200 Harbor Freight blast cabinet, but for just a few guns you can outsource the blasting to a Blasting Shop.
Before I got a cabinet, I gave the parts to a guy with a shop, told him what grit and pressure to use, and he charged me $25. ( And there were a lot of small parts and a half dozen magazine bodies).
The sandblasting is a big part of it, helping it to adhere, as is the oven curing.
I sandblasted the stock on one Mini, then sprayed it with Brownell's spray can oven cure, and it held up very well for two years, until I decided to blast it off and re-spray with FDE Cerakote. I thought I was never going to get that Brownell's Aluma Hyde off, it is tough when sprayed after sand blasting.
Another thing that makes the Cerakote so good, besides the durability, is how thin it goes on.
Rattle can paint jobs are exterior only, as they go on thick. Cerakote properly applied, only adds .001" to .0015", so it can be used on every single part, sears, bolts, hammers, etc. without affecting function. It slows down wear as the moving parts are rubbing against Cerakote, not metal to metal.
Parts like the op-rod and contact point on the bolt will show a burnished spot, but some Cerakote is still there protecting things.
There is some Teflon in the formula, so less dirt and grit attracting lube is needed, and clean up is easier, as fouling won't stick to the coating as bad as it will on bare metal.
Pics of the Mini-30 parts after a few thousand rounds, showing very slight rub spots where there is contact and friction: