I'm not talking training elites, but someone who meets a couple of time a week for a 3:00 marathoner? What is a reasonable fee for a decent coach?
If you're in a group situation, I've seen rates around $5 or $10/month, for once a week speedwork with the coach writing the workouts and timing them.
Then again, my club had cross country and track workouts 2 or 3 times a week, with volunteer coaches (USATF Level 1 certified, but no big time training), all abilities of runners, for free.
One-on-one coaching, I have no idea what that would cost - for 3 hour marathoning, I'd think that training with a group would be preferable.
I agree with idealist. Find a training group in your area and you'll probably find some other people who are training for a marathon. The trick is to find a large enough group where your chances of finding someone who runs your pace is greater! Coaches can help motivate you, but if you're not an elite or self-motivated like many people on these threads, I would find a few people with some similar marathon goals and hook up with them!