Used to be even 10 sats before the recent changes for @elvismercury:

Initially, when I created this bot, this option in the post link options did not exist. This means that @hn initially paid 11 sats per post (1 for the post + 10 for the immediate comment).

Then I could have used the post link options as you described to save 10 sats. But then we removed escalating costs so it's still down from 11 sats to 2 sats per post :)

PS: I once even accidentally drained the whole balance of @hn because two instances were running and they were consistently eating the escalating fee because they posted the same stuff at the same time so my duplicate check didn't work, lol. But I think it was max 10k sats or something that I donated to SN this way :)