What does Fowler give you for $18 million? I asked a guy I work with what's the difference between Fowler and Eaton outside of Age. Without checking stats, we agreed none. We also couldn't see paying anywhere near $18 million for Fowler per year even on a short term deal. Neither one of us though a Qualifying offer was prudent.
We're talking about a false equivalence here though. For one, Eaton is obviously younger and on his rookie deal. But if we're seriously having this conversation, Fowler has shown considerably more power. He's been a 15ish HR guy over a full season. Admittedly, Fowler has a lot of injuries that set that back some. Eaton has 16 career HRs in 1480 PAs or roughly 2+ years. Fowler is also a not insignificant 20ish points higher in OBP over his career.
But largely aside from that the point here is it's not a matter of Eaton or Fowler. It's a matter of Fowler and what few choices you have in FA. The fact of the matter is most FA's are bad investments when compared players who either are on rookie deals or were signed while still under team control. So, you can suggest Fowler isn't worth $18 mil/year but really if you're a team who has nothing at CF which could be any number of teams, you don't have a ton of choices.
Edit: Just to further my point above these teams have CF with less than 2 fWAR right now
Braves, Marlins, Mets, Nats, Indians, Tigers, Twins, Brewers, Cardinals, Astros, A's, Mariners, Rangers, Giants and Padres.