For a startup I ran, we too built an HPC cluster on AWS. It was very much a big win, as sourcing and installing that amount of kit would have been far too much upfront.

I should have really mentioned your(our) use case, as smallish department without dedicated access to a cluster or people who can run a real steel cluster.

AWS's one click lustre clustre service (FSx) combined with Batch is a really quick and powerful basic HPC cluster.

Before we got bought out, we had planned for creating a "base load" of real steel machines to process the continuous jobs, and spin up the rest of the cluster as and when demand needed