$600 was when I was working in a big tech job and while I had a sponsor page I didn't promote it whatsoever. I was surprised people were even willing to give that much given it was obvious I was making good money at my day job.
Now that this is a full time gig for me this has more than quadrupled—this post is a couple of weeks old. Also because I'm offering perks for the first time for people that pitch in. Still not enough to really make a living, but like I said in the post I have a few avenues I am trying out for revenue. I just hope that I can find something that maximizes the time I spend on the OSS tools while being sustainable.
Do not ignore the marketing and (especially) sales part. You're going to be running a business and just the fact that your software is genuinely useful and popular will not bring in the money.
Don't shy away from pitching companies you see using your tools to pay (note it's a sales pitch: a "here's actual value you get for your spend", not "support us, it's the moral thing to do")
Thanks for working on open source and good luck with this!