Oh you say that about all the Sox players. But a player’s true value in a trade depends on only two things, neither of which can be quantified statistically (although they might be justified that way).
The only true factors to determine trade value are
1) How badly Team A wants to acquire the player, and
2) How badly Team B wants to keep the player.
If the Mariners really want Vazquez, they offer more for him. If they don’t want him that much, they offer less and move on if it doesn’t meet the Sox demands...