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