You can easily use pg_dump to do a "vanilla" backup to s3. Its a managed db service but if you wanted to run your own you can extract your data and move to a new db. The lock is not "complete" you are acting like you can't even extract your data.
RDS makes it very inconvenient to do anything other than use their managed services.
because RDS backup data storage is VERY EXPENSIVE even compared to s3. this is very deliberate.
Anyone else have any idea if there's a better option??