That isn't the test at all though. When does a young unproven anything get back a significant return? (I'm not even going to discuss all of the other trades quite correctly brought up here.)
If a player is highly thought of, he's got strong value, regardless of his position. If he's not playing well or not thought highly of, then he isn't worth much.
Is Jeff Hereema worth much? Rico Fata? Michael Henriech? They were all top ten picks. They all busted. Are you telling me that teams can get a lot for them but not for a good goalie prospect?
The problem with taking goalies high is that it takes a long time to develop one, and because you can only develop a few at a time. But even with the Rangers 'glut' of goalies, a logjam seems highly unlikely. Look at Ahonen, the Devils have stashed him in the AHL for years as quality depth. If they tried to trade him tomorrow, do you think they'd get some good offers? I sure do. And he hasn't even put up 'Jason Labarberra' numbers, to say nothing of Lundqvist or Montoya's accomplishments.
Again, bottom line, if there was no downside to taking BPA.