Jake Peavy has been ineffective for most of this season. He's not signed for next year. He makes a lot of money. As such, it would seem that his value was down, and it wouldn't take a lot to acquire him. The Giants gave up left-handed starting pitcher Edwin Escobar and right-handed reliever Heath Hembree. Your definition of "a lot" may vary. I don't think it's unreasonable.
Assuming Peavy isn't awful, which he's been for most of the year.
Escobar was supposed to be the starting pitcher in a glass case, the one already on the 40-man roster who was going to push Ryan Vogelsong or Tim Lincecum for a rotation spot any day now. It never happened, and he looked awful from the start of spring training. Fresno is certainly a harder place to pitch than Richmond, but that still doesn't explain everything:
The situation reminds me of Tim Alderson, the Giants #2 prospect at the time, whose trade made me throw up frothy prospect bile. The Giants had reservations about him, suggesting his slide wasn't just a blip. The main difference is that Freddy Sanchez was good, and that wasn't really the question. Even if the Giants gave up what we thought was a lot, Sanchez was very much a known quantity. Peavy is not.
Heath Hembree has been the closer-in-waiting since Greg Minton, so it's weird to imagine him never getting a save for the Giants. The hard-throwing righty is still throwing hard and striking fools out, and his control is showing a little improvement. The 25-year-old has a career K/9 of 11.2, and if he's healthy, he should be a cheap, cost-controlled reliever for a while. That written, it's hard to imagine ever getting worked up over a minor league reliever going in a trade. Upset, disappointed, sure. But relievers will never be light-car-on-fire fodder.
Long story short: Escobar was having a down year, and Hembree was a valuable prospect who wasn't essential. Yet I still think the Giants gave up too much. Peavy hasn't been good this year. Every time I think, "Well, Escobar was having a lost season," I correct myself and think about how Peavy hasn't been good this year. I don't think the Giants overpaid relative to the market -- the Cardinals reportedly wanted Peavy, too -- they just overpaid relative to their needs and organizational depth.
If they were going to do that, then, you have to think the worst about Matt Cain. The Giants have to think there's a chance he's not going to contribute much this season, which is a horrifying thought. Not because he's been great -- he's been the most Jake Peavy in baseball, aside from Jake Peavy -- but because, well, we're used to seeing him make every start and we like the guy.
I'm not sure if Escobar's absolute ceiling is more than a Chris Capuano or John Danks, and if that's true, I'm not sure if he has more than a 10- or 20-percent chance to reach that ceiling. So freaking out probably isn't in order. Wondering if Peavy is any good, though? That's the real concern. He was pretty good last year, but last year was a long time ago.