Sounds like highway robbery to me. A quick look on Amazon and there are exercise bikes under $100, and fancy exercise bikes in the $200-$500 range. And those are one time purchases, no monthly subscription required.
If I want to go to a gym, my health insurance offers a multi-gym membership that's about $30/month. That would get me into several local gyms, a few 24-hour chain gyms, and the Y, so access to bikes, treadmills, weights, and swimming pools.
I'll admit I don't understand the concept of exercise bike classes. I mean, I've known how to ride a real bike since I was about 6, what more do I really need to learn about riding one that doesn't go anywhere and can't fall over?