1. support content I read
2. but not blow my monthly budget by paying a fixed price per piece
3. and not support clickbait junk just because I was linked to it and read it
So from a monthly a budget of $20, a couple really good posts might get $1 or $2. NYTimes CPM is $8 (or $0.008 per ad view) [2] so even $0.05 - $0.10 for an average article beats top-end ad revenues, except for sites with highly targeted audiences (assuming no one clicks the ads, which is almost entirely the case for certain audiences that might care about high quality content).
But I wasn't able to get Flattr to accept my credit card. Wasn't sure if it was because they are Sweden-based and I am in the US, as I didn't keep trying.