An old airboater taught me a trick about extending the life of EMT metal works. He drilled small weep holes at the lowest point of every member to allow moisture to escape. He insisted on drilling the holes before any protective coating or paint was applied.
There are several powdercoaters - the number is growing - who do good work. Mark Jurnigan in Plant City, FL is an example.
I believe the costs are getting closer if you properly blast, prime and sand the cage and stand before painting. Powder coating sure looks better. I've veen heard about clearcoating the powdercoated surfaces. That sounds like overkill, but, I don't know enough to say.