The Yanks were able to get A-Rod, when the Sox couldn't, because the Rangers were willing to pay more of A-Rod's contract for the Yanks. Why? Because the player they were getting from the Yanks (Soriano) had a much cheaper contract than the player they were getting from the Sox (Ramirez). It's that simple. Actually, the issue was that A-Rod would have been accepting a pay cut to go to the Red Sox & the player's union wouldn't allow it.
That's why A-Rod is in a Yanks uniform & not a BoSox one.
Actually, the issue was that A-Rod would have been accepting a pay cut to go to the Red Sox & the player's union wouldn't allow it. Yes, he would have had to accept a pay cut because the Sox didn't want to pay his full salary and the Rangers weren't picking up a lot of his salary like they are doing for the Yankees, for the reasons I noted.