Yes, but with a gym, you can switch if you keep seeing overcrowdedness. Not so with an ISP that has a monopoly.
Oversubscribing is a vastly preferable economic solution in this case. Everyone who can pay a small amount gets access to the network, and most of the time they get the bandwidth they need.
Selling a limited number of tickets at a massively increased price, or selling a massive number of tickets each with a dedicated data rate that was almost always idle are both strictly inferior solutions by very wide margins.
That throttling is essential to network management is undisputed. There were even carve outs in the old NN refs for it. The problem is if the “throttling” is not just limited video streams in general during peak times, but actually just limiting just certain services’ streams.
And this is the real problem.
The U.S. should require access-network sharing (at least for fixed-line, mobile seems to limitations here), like most other countries do ...
Then you wouldn't need to over-regulate how ISPs operate ... you could let the market decide.
A guaranteed 1 gig circuit is on the order of thousands USD month. An oversubscribed consumer fiber provider like Google Fiber is an order of magnitude cheaper because they can oversubscribe based on consumer traffic models that cover 99% of users.
Also keep in mind that your model isn't really straightforward at all. The ISP can only provide you guarantees within the lines they control. There could be any number of choke points at IXPs that mean the user can't reach site X at their guaranteed rate. So ISPs never even offer hard guarantees on connections to the wider Internet. The most you will be able to buy is dedicated circuits to their core, an IXP, some branch office, etc.
Are you okay with gyms selling more unlimited memberships than the number of machines they have?