The detail
Tweets are capped by characters, not words, so it is easiest to anchor on the 280-character limit. A packed 280-character English post is about 45–50 words, which lands near 60–70 tokens. Most posts are shorter and run 15–40 tokens.
Hashtags, @mentions, and URLs change the math: a shortened link is a handful of tokens, while a long unshortened URL can be a dozen or more. Emoji are typically one to three tokens each.
If you are building a tool that classifies or generates social posts at scale, the per-post token cost is tiny, but it multiplies fast across millions of posts — count a representative sample to project spend.