This leads to the problem of stopping to pay once the feature you care about exists. Software is an interesting problem where you build once sell a lot. It's not economical if you sell once and give the rest for free. There are a lot of software products that I use, that I don't personally need more features for, so I would have no incentive to pay. My usefulness has been subsidized by others.

In other words, I don't think it's a sustainable way to support open source projects

I used Ghost.org in a project last year and love their business model (and obviously their product).

Completely open source software, but you can pay a reasonable amount for managed hosting and support. Plus obviously it supports the devs and new development.

A simple line to separate DIYers from anyone who wants the convenience, peace of mind, or to support the project itself. Would love to see more of this.