1. Types of influencers
The number of creators' followers affect their posts' cost. Less followers-less cost. Therefore, posts of celebrities are the most expensive. But it's not reflected on the campaign effectiveness.
Nano and micro social media influencers have not less power than celebrities. They create more unusual and interesting content. Their posts often bring better results because they have a more engaged audience. Besides, micro-influencers followers frequently better match with brands' target audience. It happens due to the fact that they have a certain niche of interests.
If you are, for example, a cosmetic brand and your target audience constitute women at the age of 25 it's better to use micro-influencers in the beauty industry. As celebrities commonly have a lot of teenager followers, the audience of beauty-bloggers will be more relevant to your target audience.