I'm resurrecting this thread because I also just "discovered" the small balance credit, and wanted to share.
I have ten or twelve rarely-used credit cards, and got a notice from the bank to use it or it would be cancelled. I used it to buy a bagel from Panera for $0.89. And when the bill came, there it was: the "Small Balance Credit". Over the next few billing cycles, we tried charging various other amounts, and eventually nailed the threshold at $1.99 for our Wells Fargo card. So, once a month, we used this card to get something small for free.
And then, we accidentally did the same thing on another rarely-used card. So I looked it up on MrMoMu, and found this thread.
Look, this is way more work than it's worth. This is not a wealth-building strategy, or even a money-saving strategy. It's a couple of bucks. But this is how we roll in Phildonnia.
We now have a box with our rarely-used cards, separated by $0.99 and $1.99 thresholds, so we can just pick one up whenever we are going out to get a burrito at Taco Bell. The "used" card then goes into the back of the box, until the statement cutoff date, when it gets moved back to the "available" pile.
This site may be a helpful guide, though it's not completely accurate:
https://www.doctorofcredit.com/small-balance-waiver-a-k-a-lots-of-free-99-cent-amazon-gcs/