Well if it's any consolation, I wouldn't sell mine for half again as much as I paid for it and I don't think you will regret it, if you do get one.
Further, although I don't think I should/could call myself a "professional" I do make a bit of extra money with photography, and the lens has pretty much paid for itself already. I surely can't make any comparison of image quality between the 80-400 to the latest 400 f2.8, that almost $9000 price tag for the latter sure is a major stopper for a lens that I can’t use on a fairly constant basis like the 80-400 and that doesn’t even get into the lug factor. Not that I don’t lust mightily after more than a few of the ultrafast long lenses.
Later Larry