That's exactly what most PBN sellers here do. And it's a blatant scam and a ban reason as well. So yeah, "there's money to be made" and also "ban to be hammered".
But let's break it down:
Bought one time package PBN links: They drop mostly in less than a year, mostly on crappy domains, once links get lost, they do more damage than good.
Rented PBN links: Nobody would rent a link for $360 a month for a site that's not raking that kind of money in a day. You can get decent rented links for a few bucks. No idea why we go to the extremes here.
Your own PBN: Quality domain compared to the ones that decent link renters have is at least good $300. I would price a link on this one to maybe $10 a month. That, plus hosting, plus content. 10 sites like this one and you end up on good $5K for the first year. Renting 10 links like this is $1200 a year.
So it all comes down to what you consider more effective, safer and better for your overall ROI. If I were to buy PBN links nowadays, I would buy only rented ones.