Terp, I get where you're coming from here, but I think you're seriously underestimating the difference of "a few million." Sure, to you and me it seems like it's so much that there's little difference, but that doesn't mean that athletes (like any other high-earning, short-term profession) shouldn't maximize their earning potential over the lifetime of their careers. As with any employment decision, you'd expect the player to want to weigh the full situation, including how much he likes playing there, chances for non-monetary compensation (championship!), etc. But at the end of the day, if I'm his agent, and the Nats offer 2/28 with a mutual option at 15m, and the Braves offer 4/52, I'm telling him to take his talents to Atlanta.
As I said weeks ago, I'm all in favor of resigning him, but I think his cost is going to be so high that it's worth taking a hard look at Greinke in comparison. Where I think my opinion is changing is that I'm not sure why we wouldn't want EJ on a 4-year deal*. The #1 underrated factor for the Nats this year is health of the starting pitching. The Nats have had only seven guys start games for them this year, and one of those (Lannan) was only because of the way the schedule fell. Put another way, of 112 games so far, only 6 have been started by somebody other than the normal starting 5 - that's an amazing run of health. If you're shutting Stras down and playing for the long playoff run then you have to do everything you can to insure that you can compete in years where you're not as lucky as we have been this year with pitcher health. EJ would be a big step in that direction.
*- and before somebody throws the list of pitching prospects at me, yes, I know Solis, Purke, Meyer, Giolito, etc. But how many of those guys are really going to be better than EJ? How many of them will be better than EJ in the next 2-3 years? The other major underrated factor of EJ is that he's 28. Feels much older because he's been around so long, but he's easily got 4-5 more years of prime pitching left.