All the reports make me think something like this:
Hamels costs a top prospect -- Betts, Bogaerts, Owens or Swihart, plus one or two guys from the second tier.
Cueto costs two or three second tier guys like Devers/Barnes/Ranaudo/Eduardo. Cespedes could potentially replace one of them.
Price costs one player who will impact the majors immediately, like Betts, Bogaerts. It could also be a player like Cespedes or Castillo, but with a second tier prospect included.
Zimmerman will cost something similar to Cueto or Price.
Fister/Leake/Latos/Porcello will cost something like a second tier prospect + a high ceiling throw-in, or Cespedes + a high ceiling throw-in.
Ben is waiting to get one of Price/Cueto/Zimmerman/Hamels for Cespedes + a second tier prospect. It might cost more, but there are enough sellers out there that he is bound to find a deal he likes.