Cerakote might be half the cost to do, but I would have to say it isn't even close to half as good as the value of DiamondBLACK. If you figure out how much faster it wears out, there is no comparing the cost savings of going with a higher quality finish. Cerakote is a local company and I think they are the best of the paints I've tested, but if you want it to last and it is going to see wear, it still will not hold up to heavy use. I wish it would as it is very cheap and simple to do.
Toss a Cerkote magazine across a concrete floor (ie indoor range) and do the same with a DiamondBLACK mag and that is the only test you'll ever need to do.