I do really like Nylas, it's mostly a pleasure to use.
But I'm using it with Gmail which costs me like $2pm for 100GB storage; the core (with I think 20GB?) is free (at the point of use, blah-blah advertising).
Is Nylas, the thing through which I access my free/almost-free email really adding $12pm value? I'm not so sure.
At $7/month, if this tool saves you 10 minutes a month, it's worth it.
Essentially, we started as a free beta at the very beginning, launched with free trial last year, and now have switched to freemium (with a free trial on the Pro version still there).
Does that make sense?
(I work at Nylas.)
The Nylas client doesn't connect to you mail provider directly, instead the Nylas client connects to the Nylas Sync Engine. It used to be that using this API for this was a couple hundred a year, per account.
Both the client and the sync engine are open source, so you've always been able to host your own.