There are a lot of assumptions made within that post.
Bubble doesn’t state a limit, so it should not be assumed they would limit the number of apps that can be hosted on a dedicated server.
Since the OP mentions some sites may need to interface with an API as that is unknown, you can not assume all apps are the same, so a subapp approach may not be the right choice.
This assumes $38K a year might not be good enough profit to make something worthwhile and that the overall concept does not involve it being more of a passive income.
Again assumes all apps are basically same.
This assumes the single app that powers 100 apps can scale on a non dedicated plan, which may or may not be true.
Dedicated plans can be beefed up with more resources if needed. The only pricing info I have is from Bubble pdf on dedicated plans that I’m 2018 start at around $1,100 a month which likely has increased.
Either way, my response wasn’t meant to provide commentary or provide business advice, I simply chimed in to answer the question in the title for how to host 50-100 apps on Bubble not using an Agency account. Hopefully it helps answer the question and gives OP options to explore on whether or not to proceed with his concept.