JavaScript API pricing is dangerous. Here is why
dokeeno.com
dokeeno.com
I'm glad you like Mixpanel! This is certainly something we've considered, but (at least for us) the usage-based api makes the most sense. Unfortunately you can't avoid this kind of thing once you go the usage-based path, but it hasn't been an issue in practice.
We've never had a malicious user manipulate someone's data (and it would be pretty obvious if they did). If it did happen, we wouldn't charge them for it.
Alternatively, if you understand the consequences of using an unofficial API, and your web service has the bandwidth to do so, you can trigger the API by manually stimulating server-side REST requests identical to what the JS API does.