One day, many years ago, in a panic of "how the hell do I make this scale: I need it to work right now" I replaced an infrequently read data logging setup I had with S3... I ended up spending >$100k storing keys into that thing and momentarily was 2% of all objects stored in S3 (based on the stats they occasionally provided) before I eventually (two or three years later?) retired it; and to be extremely honest and to add insult to injury, my read access was so "infrequent" that I think I just never ended up reading it again after that day :/.
Yes. I should include this info in the README calcs. For my usecase I intend to do 4 - 10 PUTs per hour, since they are batched. 10 PUTS/h = 7300 PUTs/month = $0.073/month. The key here is infrequent
Be most careful with retries. Saw a case where the bucket wasn't writable and the code just retried in a loop. You get charged for the API call, successful or not.