Never done it, but I get emails from the Celtics with info about them. It's crazy expensive. The suites hold about 18-20 people, and the price varies depending on the night and opponent, so you'd pay the least for a Tuesday against Philly, something like that.
For the cheapest games, a suite including food is gonna run you over $2500. The Lakers and the midseason Heat game are over $10 grand, and opening night simply says "Call for Pricing." I think you know what that means.
Anyway, a Friday night game against a random team would probably run you $200 per person.