Wouldn't that risk the account though? I heard YouTube is very strict and searches for inorganic subscribers etc because they consider subscribers and views as money. My two cents, because I've seen one of my friends account got banned after he exchanged in a "sub for sub" forum.
Of course if your channel is provided by fake activity, like likes and subscribers, your channel is screwed, but there are other domains that provide you with real subscribers, like a friend of mine that was struggling to start his channel, was stuck at 600 subscribers, and he wouldn't take the risk to buy subscribers thinking he would get banned, but then I found a domain
https://www.subscribers.video where he was provided with REAL subscribers, he couldn't beleive it ! his channel went from 650 subs to 1500 in just 1 week !!!! and his channel is now naturally growing its activity, so definitely buying is risky, you just have to know where to do it.