Yeah, that makes a big difference, especially considering that the draft is a very inexact science and somewhat of a crapshoot. The Yankees have picked up some pretty good young players outside of the draft, e.g. Cano and Wang. Here's a link of first round draft choices since 2000. It demonstrates just what a crapshoot the draft is. These are first round picks and not that many guys make it to the majors, and very few become stars.
http://mlb.mlb.com/NASApp/mlb/mlb/history/draft/index.jsp?feature=decade2000s
Here are the first round picks from the 90's
http://mlb.mlb.com/NASApp/mlb/mlb/history/draft/index.jsp?feature=decade1990s
Letting established stars walk to get draft picks is not much better than getting a lottery ticket in return, and if the picks aren't in the first round the odds are way worse.