Yes, of course you might be CPU bound, in which case even a single user might take up 50k servers (think of a scientist doing a climate simulation, or an AI res

Yes, of course you might be CPU bound, in which case even a single user might take up 50k servers (think of a scientist doing a climate simulation, or an AI researcher building a very large model). All things being equal, CPU-bound is the exception, not the rule. Most every program we think of as an "application" is chat with some structure, persistence, access control added, and are indeed IO bound.