Granted, $150/month is a lot of money but there's no way I'd drive down to the gym, open it up, and spend and hour and a half of my time teaching some beginner to box for ten bucks an hour. A gym like Gold's or 24hour Fitness charges $65-$75 per hour for personal training. Just call around to some gyms in your area and see what they charge. If one-on-one lessons cost too much maybe there are some small group classes you can get into. I wouldn't recommend trying to do it all on your own though.
Edit: it may be that the prices you saw were just for the gym membership and not for training.