well, the value depends on how much money you have made, and calculates a multiple off of that based on the estimated future earning potential.

e.g. if you have 1 brand that paid $500 you for a collab to your 100k followers - then the valuation multiple would be maybe 2x of the $500 since theres no guarentee you could even get the same brand to give you $500 again, let alone twice. why 2x and not 1x then? you might argue the time and time-cost of getting 100k followers justifies at least $500 due to the time and time-cost the buyer saves.

on the other hand, lets say you have a brand where contractually they have agreed $500 per post, and 1 post per month for the next 3 years, and you’re selling at month 1 of the agreement - then your valuation would be higher maybe - 500x12x3x5 - why x5? one might estimate if i can do that with 1 brand, i can probably get 4 more in that time frame of 3 years

bear in mine this is oversimplified, but it should give you and idea of how one would value your business, you should also bear in mind valuation is almost totally subjective opinion, but it is underpinned by facts.

other things to consider are - the risk of your account being banned or blocked, the risk of your followers all leaving, the risk all your followers are fake, the risk brands no longer want to work with influencers - these risks would all factor in a buyers consideration of the value of the business.