Then you have the flipside of those deals, like when the Giants gave up a fortune to get Eli. Yeah, you can argue that Eli wasn't worth it, but two rings are two rings.
Ultimately, huge moves are judged less by how that particular player turns out and more by the overall team success going forward which is exactly how they should be viewed.
Julio Jones is an all-time great WR, but the Falcons really shackled themselves by giving up that much to get a WR. Had they not blown that 28-3 lead, the move would be viewed differently.