I agree. I don't think hero and legendary members will sell their merits, they aren't that stupid.
The most important thing is doing this will put their accounts under extremely high risks of red tags, bans by admin or forum mods.
They won't foolishly do this to get additional several hundreds of dollars.
However, there are also several higher ranked users who don't care about signature campaigns, bounties. They simply do their jobs in the forum.