How are all these teams getting players such as Victor Martinez, Cliff Lee, Jake Peavy ... and so on..... without giving up their main prospects?

The Sox got Martinez w/out giving up Buchholz or Bowden.  The Phillies got Lee w/out giving up Drabek, Brown or Taylor.  The White Sox got Peavy w/out giving up Beckham.  And I'm not even listing the numerous other smaller trades.  It makes me think what we would have to give up to be in the discussion. 

If we labeled a few prospects as untouchable (say Castro, Norris & Lyles) could we have been in the discussion?  What are players like Ross Seaton, Jonathan Gaston, Yorman Bazardo, J.R. Towles, Brian Bogusevic, Chai-Jen Lo ... worth?

I'm not saying I want to trade all those guy's ... but if stars were going for so cheap.. couldn't we have at least entered the conversation with a few of those names?  Couldn't we be in the conversation for a Scott Kazmir or maybe a Matt Capps?

What do y'all think?  I'm just trying to understand my confusion.