We circumvent Mixpanel's limited events early on and stayed under their free tier for as long as we could. This is what our setup looks like:

We collect millions of data points a month and save them on our servers. We do not use Mixpanel's SDK to collect these data points, but have written our own code for that. We save the raw data on our server, aggregate a bunch of similar events to 1 event and then push it to Mixpanel using their API. We heavily use event properties to send as few events to Mixpanel as possible.

This way we get most of the data into Mixpanel and can build funnels, etc. without any issue. There are some edge cases where we aggregated data is a limitation. But for those cases, we end up using the raw data that we store.

Not sure about your use case, but hope this helps.