I train at Redline Fight Sports in Cambridge, MA and they've got some pretty sweet prices. It's basically a sliding scale where you'll pay less per month, the longer you sign up. You can sign up for 12 months, 7 months, 4 months, or 1 month. 1 month is pretty expensive, but 12 months is a STEAL!
It's wicked flexible too. There are 5 different programs -- MMA unlimited (where you can take any class), Kickboxing, Boxing, BJJ, and Fighter Fitness (conditioning). If you sign up for a year in the MMA program, it's 115 a month which is the best deal in the area. The gym is open all day and there's morning, noon time, and evening classes. Between all the different programs, there's always striking (boxing or Sanda), grappling (Wrestling or BJJ), and conditioning classes every night Monday-Friday. As for weekends, there's kickboxing and BJJ on Saturday and Wrestling and BJJ on Sunday. And on top of that, there's 3 MMA classes a week.
When you take student/military/police and fighter discounts into consideration, it's an amazing deal. But even the standard, non-discounted rates are the lowest you'll encounter in this area forr MMA. There are a few similarly priced gyms and some that go up to 200 +