It's strange that page mentions rate limiting of 60 requests/min, 10 requests/sec. Are you sure the pricing is 100 requests per month?
Seems pretty clear, though I can't fathom why they chose "periods" rather than "months". Crazy expensive.
[1]: https://developer.twitter.com/en/pricing/search-fullarchive
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edit: though the more I read it, the less confident I become. wtf is up with this copy.
I wonder how they can justify these prices?
That cost is then passed back on to the requester.
I mean, you've got to think someone has done an expected demand / price model and decided that this will maximize profits. Only people they need to justify to are shareholders.