Assuming the creators go into these deals eyes open I can see the appeal of making an exit from the grind. It's hard to spin up a business outside of the platforms without access to resources or other income. One person bands will burn out trying to manage merch, algorithm optimisation and content generation at the same time.
I can think of a few channels that have gone interdependent but I'm sure they get income from other places as well.
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On the actual topic I know a number of people getting injection privately and swearing by the results. There is a pretty aggressive referral campaign as well which considering the monthly cost is going up you can see why people will sing it's praises.