Cost depends on what I'm doing, the color, what the current condition of the part is, etc. doing a generalized cost doesn't work to well, as every job varies slightly.
As for hot parts, I use Cerakote
Turn around time depends on the workload I have at the time, as well as what you are wanting done. If it's small stuff, I can bust out in a day. A set of wheels is usually 2 days.
I do have a lot of powder on hand, but I may not always have what you want on hand. So I need time to get specific color choices in.