the cost of any training [group class, one-to-one, training vs B-Mod for problem behaviors, special interest, dog sport...] can vary wildly, plus where U live makes a difference in pricing / costs.
Basically, trainers charge what the market will bear; cheap might be good, lousy, or okay training, as the instructor's skill in not only work with dogs but ability to explain, demonstrate, or otherwise convey knowledge will also vary among individuals.
The most-expensive local trainer might not be the "best", but might be very good at marketing, or they're cashing in on a currently popular activity [disc dog, bike-jor, dock diving...] that draws a lot of business.
I would avoid anyone who keeps citronella spray or beanbags on hand, personally.
Behavioral fallout is generally a lot harder to fix than the original problem - whatever that was.