Scratching my head on this one. Obviously a Prevost is a better MH than a Thor, but consider; to get a Prevost at that price you'd probably be looking at something 20 years old. Despite quality, there are a lot of things at that point that would either be falling apart, in disrepair, need of replacement, outdated, or all of these. You could get a brand new DP from Thor under warranty at that price. Again, would never argue the quality comparison, but Prevosts and their parts aren't immune to issues any more than any other RV, especially 20 years old with a few hundred thousand miles.
That said, you can get a nice, used - but much newer - MH, say a Newmar or something , in your price range.