I don't think there's any single piece of transmog that could come out of salvage boxes worth 500k. Most BoE transmog would top out at about 120k for the best stuff.
None of the slutmog goes for high prices anymore.
Relative to what they used to go for
I've seen glorious pieces going for 400k in the last month and the new system will just increase demand, especially initially. I expect all that stuff to spike significantly with 7.0.