You can roll your own too with the terraform code in it. It costs me barely anything (never go over free tier limit) to run it because files never live more than 10 days (there is a catchall lifecycle rule on the bucket) and when users select durations, i also put them in bucket prefix that has lifecycle rule place on objects under them for that duration. Note that we can't rely on lifecycle rule all the time so i also make sure when lambda is called to access the object, it checks the time-stamp, the duration and if it is meant to expire and not yet cleaned up by s3 - lambda function deletes it.
I learnt a ton of cool things about s3 after this neat little project and really dig the API, the lifecycle rule, signing url etc...
Ps: for these type of tool, you should definitely mitm it to see if plaintext file or password ever leave the browser... Relaysecret does leave one item unencrypted and that is the file name. You can change it upon upload but i like to leave it there so people know what they are downloading. I have simple idea of encrypting that with just the anchor key but haven't gotten around to put that in yet.