Slight rant - the itext license change was frustrating because we were using it on a project, and then the license change happened. The minimum price seems to be $2500, and I couldn't tell if it was per year or what. But to have it on a dev machine, and a test server too, drove the price up more - something close to $6000 IIRC (but it's been a while since I looked in to it).
I completely understand the motivation behind the pricing changes, and if it turns out that fewer people use it, but they pay... that still works out for most parties.
I'd encourage the nodemailer author to consider a couple other options - something under $500 for commercial usage, and a higher price point for some extra degree of support (1 business day turnaround time, etc?). As others have noted, a smaller amount is something I can float or simply absorb - larger amounts introduce hesitation, or pushback from clients on pricing (especially if it's a term/time license).
We don't use Nodemailer, but we might now that I know about it. I'll see if we have a use case.
Might want to also offer a premium release for 10x or even 20x, since that falls into the "No Brainer" category for larger corporations who would look at 800 as a sign of low quality.
If you want companies to pay you, then ask them to pay you. Keep it as a simple license (not one that has devs asking wtf it is), but offer a commercial bundle with email and dev support, LTS, backwards compat and perhaps authentication modules (for LDAP/AD, OAuth) and I think you'd be surprised by just how many companies make these purchases (I make them all the time).
Also, on price - $100-300 is "no-brainer i'll put it on my credit card and expense it at the end of the month" while €800 is approaching purchasing decision territory for a lot of companies.