Because they believe they are getting value through the some combination of equipment, exercise, leadership and community. It has worked for a long time, most recently with BeachBody, Peleton, and now Apple Fitness+.
When you take a minute to understand why it works, you can quibble about the cost, but there's no denying that the customers are happy with what they are buying. Nobody is bamboozled into these business models.
When I was younger and had more free time, I would tinker, too, content with my saving $20 there or $200 here, ignoring that the savings were a wash considering the time involved to find these discounts. These days sometimes I just pay extra knowing I'm not getting the best deal, but I'm getting something that works out of the box without me fiddling or having to spend my precious free time outside of work reading about the exciting exercise bike industry of all things.
There are different hardware options like a regular bike on a trainer [0], or a smart bike like the Wattbike or Wahoo Kickr bike [1]. These use open standards and let you use different software, and if you use a regular bike on a trainer you can even use it outside when the weather permits.
The most popular cycling training software is Zwift, it's basically the de facto standard just like Strava by this point. But you don't have to use it.
[0] https://www.dcrainmaker.com/product-reviews/trainers
[1] https://www.dcrainmaker.com/2019/10/smart-shootout-wahookick...