It's just like any other trade. Each team has varying needs at the time, and different reasons for making the trade, but every team also makes a decision about the merits of the players on both sides, and that comes from the pro scouts. Someone decided Sanchez was an opportunity worth giving up Mead for, since the Rays didn't want to keep him on their 40, and that's fine. But the scouting reports were still part of that decision.
Ragsdale, on other hand was traded for nothing, just a way to get the Sox to pick up Workman's salary. So they valued CBT room over him, and/or valued him less than other players the Sox might have wanted.
