I looked into getting a set of Velo cases and rocker boxes vapour blasted recently. I chose someone quite close to home and who said (on his web-site) that he specialised in classic car and bike parts cleaning. When I asked him for a rough estimate he said £150-200 which I found astounding.
He said that it wasn't dear, that was the going rate for the job, and if I could get it cheaper somewhere then good luck and go forth and multiply.
Not really that expensive, is it? Cleaning cases, like stripping paint from frames, is one of those jobs I'd happily pay someone else to do every time, if they were reasonably priced.