let's crack it, any successful YT channel need REAL & ACTIVE subscribers, there are 2 ways to get them
1. the hard way, with hard work SEO, SEM, viral content etc.
2. the easy way, to try to buy them on the marketplace, but those can be dummy subscribers of a bot accounts, that will only effect the subs count
as you need REAL & ACTIVE subscribers, you will need to find a provider that have a unique method to get REAL & ACTIVE subscribers (not by using fake YT accounts bots)
and then after your find him, you must get ONLY 1000 subs to check the quality (even on another channel) if they active you will know it.
again this is a hypothetical discussion, i think that the cost of REAL & ACTIVE subscribers will be high, even that some of them may un-sub or un-like your content, since they will 'not-remembered" how they subscribed to you in the first place, but if your content is generally interested and unique or Music, it can be gold.