The way I come to look on such offers (monthly unlimited subscriptions) is not the net price itself, and not future supposed returns to it (who knows what they be, and they for sure will depend on many other things), but how many hours a week I am willing to spend on that service.
If you can and willing dedicate on average 2 hours a day (a big commitment but I think I was able to hold it for several month with them) the cost of mastering, say, Linear Algebra will be ~4 less then if you subscribe and will be spending ~30 minutes a day.
For sure Bezos handled this badly. But the problem in my opinion is not his management skills or even his civic valor, but apparent fear of business and public people of retributions for supporting a wrong candidate.
I am happy Math Academy customer. Agree with most what you wrote above.
Except for the pricing estimate for the private tutor and related 26x cheaper comparison.
People generally don't hire private tutors to have lessons every workday of the week. No I think it would make sense for do so even leaving out financial cost.
It is more like once a week session with take away homework (maybe twice a week for a quite intense level). This brings cost comparison down to the 5x time (10x for twice a week). Still quite impressive.
As others have already mentioned this is used in a lot (most?) of databases.
It is called "slotted-page". Searching for it gives good discussions/explanations of it.
If you can and willing dedicate on average 2 hours a day (a big commitment but I think I was able to hold it for several month with them) the cost of mastering, say, Linear Algebra will be ~4 less then if you subscribe and will be spending ~30 minutes a day.