After 20 years of maintaining open source software on multiple projects and getting $0 dollars of support I applaud the attempt to reward these professionals.
Building and maintaining "personal infrastructure" to do open source "at scale" is expensive in time (github, continuous testing, test suites, pull requests, email, DMs, phone support, etc.) and equipment (development computer, router, network connection, AWS, backups, etc.)
In addition, if your project gains traction you'll get invited to give talks. These can sometimes be overseas (yeah, I know, nobody travels anymore). The time to prepare a talk and the travel cost is another personal expense. The most I ever got from a talk was a free hoodie. But I paid for the round-trip airfare, rental car, 3 days at a hotel, and most of my meals.
On the project I've maintained for the last 20 years I estimate that I've spent about $3000 per year. That should be the "baseline" for supporting an open source project.