I just had the battery replaced in two mid-2014 MBPs. They said that I'd be paying for the battery replacement (199), but that they would also replace the keyboard and trackpad and I wouldn't be charged for either. However, the way they stated it initially was a little confusing, since it sounded like I'd be paying an additional 100, but they were quick to clear it up.

They did say that they might need to replace the shell (battery was slightly swollen in both machines) and that I'd be responsible for that cost, but that didn't happen for either box. I don't think they replace the shell unless it's really, really deformed. Neither of my machines would sit flat and both were obviously swollen. One I could practically spin like a top (and the trackpad was screwed).

I got both back with no deformities, a new battery, keyboard, and trackpad, and a 199 bill (plus tax).

I wouldn't rule out getting it fixed. If you do end up paying a little more, then you can probably sell it for more than the price it cost to fix.