AWS has systems with up to 24TiB of RAM (u-24tb1.metal) [0], but the pricing is "call us". For almost 4TiB of RAM (x1e.32xlarge), it's about $28/hr [1]
For a researcher, that means running an experiment changes from "running the experiment" to six months of meetings with higher management establishing business cases, budget justifications, getting competitive quotes from different providers, etc. (in other words it just doesn't happen).
The choice is not between "on premises" and "cloud", it's between "on premises" and "our glossy faculty brochure says you can do this but really you can't".
This struck a nerve with me. I was a SWE at a company that moved to the cloud last year, after having a couple racks at a local colo previously. I was able to experiment and iterate so much faster when we owned hardware, despite all the cloud's elasticity. After we migrated, everything was request, wait, explain, request, wait...
I know some organizations handle this really well, but when mine didn't, it sucked to be a developer there.
[0] https://aws.amazon.com/about-aws/whats-new/2019/10/now-avail... [1] https://aws.amazon.com/ec2/pricing/on-demand/