I think this gets down to the actual value of prospects and what they can get in return. Generic things like "prospects are overvalued" doesn't really say much. In a sense they are, but in a sense they really aren't. The top prospects (Sano, Buxton, Meyer, Berrios) are valued (rightly) very high, but guys like Stewart, Gordon, Thorpe, Polanco, even though they will be highly ranked in the offseason, really aren't going to bring back much in return because they are far from the majors, and a team that is rebuilding, like the Twins, are wise to keep them in their system instead of flipping them for a year or two of a corner OF. Guys ranked lower than that are guys that get half a season of a bit piece at the deadline or maybe a full year of a guy with a little too big a contract (or are third pieces of a bigger trade). Trade a prospect for a player? OK fine, sounds good in a vacuum, but what does this actually look like to you? To get a legitimate player that has more than a year of control, it starts with one of the big 4 and then needs another couple of guys as well.