Seems to have changed pricing a bit since. The 'pay as you go' model now has 2500 API calls/day for free, and $1/2000 API calls after that. My needs never grew in to needing much more than what we hit for that $5/month, so I can't vouch for their service at a large scale, but I enjoyed using it.
No affiliation just a happy former customer.
Might add up.
(And glad to hear that conference sponsorships work. A lot of smaller conferences are struggling to find sponsors these days, so if anyone reading is in a position to sponsor, the organizer of your favorite conference would probably appreciate it!)
FWIW, first time I saw you was at LonghornPHP in Austin. 2021, IIRC.
The organizer of Longhorn PHP is a friend of ours (Daniel Abernathy), and we have a somewhat official-unofficial rule that we always sponsor our friends' conferences :)