Never buy a list. Well that's what I always say and I'll mention why. Keep in mind this is my opinion and I am not telling you what to do but hear me out at least and then go make some coffee and eat dinner.
I prefer to build my email list 1 person at a time with quality content, good placement of the autoresponder box's and network with my followers to gain new subscribers as when people start to trust me, they will want to hear more of me and join my list to stay updated.
Also, I know everyone on my list is interested in my content, like my writing style and most of all trust me because if they didn't trust me, they wouldn't of opt-in to the list. This makes my list a money maker and traffic maker when I send out an offer.
If you buy a list,, chances are they are robot's or people not interested in your content as they was forced to opt-into a list or there email address was scrapped.
When people email me and I didn't opt-in to there list from there official website, I report them for spamming and block them.
Do you think Harsh or Patt Flynn bought every subscriber? No, they earned each subscriber with quality content, good networking skills and other good stuff.