PTR right now seems fine in terms of difficulty. See Old raids, level scaling and leveling chars - #15 by Xênosh-tarren-mill where both I and Xênosh concluded that the first boss in Nighthold feels about the same on live and on PTR.
I am guessing that this will still be true in pre-patch.
Beta is a very different story. Both Xênosh and I died miserably on Skorpyron Mythic when we went in on level 60s in Beta. Old raids, level scaling and leveling chars - #6 by Lommatik-draenor
That does not seem right. I think Blizzard have work to do in tuning old content for level 60s.
Gold value is VERY hard-hit, though. My few tests suggest that vendor gold is down by 63%.