$5 per 1k followers average, so $500 per post for 100k followers, sometimes split with a talent agency/network that takes a cut. Smaller accounts are worthless but might get bought as a bundle. $1k+ per post needs 1M+ followers.

$25k+ per post is just normal celebs. $250k on a social media post is extreme and only happens if the person is incredibly famous. It's no different than tv commercials and sports deals. Nothing has really changed other than adding a new medium to monetize. The fame is still the hard part, although there's more of it to go around and more opportunity for those that try.