As a first year commissioner of an auction keeper league myself, I'm not a fan of this rule. First off, many of these players should be on people's radar during the draft based on the keeper structure of the league. I'm not sure exactly how your league is set up, but my league has a couple of safety nets to prevent these situations from frustrating people. First we have a reserve roster, so a lot of the "super rookies" were drafted at the end of the draft for between $1-3 and just placed on the reserve roster. Also, all free agents are $5. So in my league Hunter Pence was picked up as a Free Agent earlier in the season at a higher price than many of the mentioned "super rookies" were drafted. I don't know if you already have something in place like this or if it would even help, but I figured I'd throw the idea out there.
"I can't drive, so im going to walk all over you." - Soda Popinsky