It’s not the numbers but the content, if they are good natured and have knowledge or entertainment to give the numbers will follow BUT people will also watch a dumpster fire. People with high numbers but lack the rest are not influencers. IMHO, People that go around saying they are “influencers” usually are not and are just bullies trying to throw around weight they don’t have to get free stuff or cause harm.
As it happens, every person is an influencer, regardless of followers (…) or content.
The people who are influenced, or said differently, the sphere of influence is dependant on random factors like content going viral when it unexpectedly gets liked and reposted by others.
If you’re asking what size of influence generates income, the answer depends on who is paying.