I've had several frames blasted to "white metal" for about $150 each.
Why people want to powdercoat frames still escapes me? ?:?
Powdercoating is great for many things, but IMO, not for frames, axles, bumpers, etc.
It is durable, but not easily repairable. Once you scratch it and rust starts it will bubble under it and lift large areas. If you ever want to weld or modify a PC'd frame you can not touch it up easily like with paint.
A properly prepped and painted frame will look as good if not better and will last if some basic care is taken. Afterall, the crappy OEM paint probably lasted 30-40+ years on yours until now.
I like PC for some engine parts (intakes, brackets, etc.), and some other parts not likely to see rock rash or need future welding or modification.
It's always cacked me up when I'd see a $50K+ custom chopper or big $ street rod boast about a PC'd frame. PC was developed as a an easy, cheap, more environmentally compliant finish for high volume production on conveyors, just like Harley does on all their bikes.
Anyway, I hope that at least the first part of my reply helped! ;D