You say your target is $500-$1000 per video and let's assume you do videos weekly. That would mean your optimistic goal is $4500 a month. Let's say you create a voluntary donation subscription at $5 per month for people willing to support your work. That means you would need 900 true fans, patrons, or whatever other label you want to give them to hit your $4500 goal. That's a 0.9% conversion rate from subscribers to donators. Doesn't seem that impractical when looked at in those terms. This is often the default monetization model for small podcasts because RSS feeds don't have built in ad revenue the way YouTube does.