The most interesting part for me is not the top-end 192 core size, but the small/medium sizes.
Looks like m9g.large is about 9% more expensive than m8g.large on-demand, at least in Vantage’s current data.
If the “up to 25% compute improvement” holds for real web/database workloads, that is a pretty reasonable perf/$ trade. The usual caveat is that small SaaS apps are often bottlenecked on DB, storage, or network long before raw CPU.