"Aurora Postgres doesn't have a filesystem for its tablespace. It has a block store. Instead, Aurora Postgres instances that are doing large sorts or indexing large files use local storage, which is currently 2x the size of memory. That is, if an Aurora database instance has 72gb of memory, you only have 144gb of temporary space. Good luck sorting that 150gb table."

That seems like a problem that's easy to overcome. Allow people to configure the local storage size and you have a reasonably fair solution.

Still has its limitations for really large datasets, but that's also one you have with vanilla postgres.