They're not only insane (i.e. offering H100s for rent at a quarter the price they'd be to purchase) they're also impossible, since every listing claims to have deployed an Infiniband fabric speed which is firmly in the future.
The IB equipped on our clusters (can't speak to others) is 8x 400 Gbps. Most customers training foundational models are able to fully utilize that fabric in parallel.
And out of curiosity, is aggregate bandwidth the normal marketing metric in this industry? In my neck of the woods this would be reported as an NDR400 system.