Yeah, such a scenario may be workable. But the egress costs would still be major concerns because if those 50k employees check the app even once a day, that's akin to 50k daily unique traffic to a website. And unlike a website, the app wouldnt be able to offload majority of traffic to a CDN like Cloudflare since its unlikely that it will be serving static content. So egress costs alone could be a game breaker for that.

Generally speaking, the main cloud providers are still applying the network prices of mid 2000s to their clients. Hopefully with Hetzner opening up a datacenter in the US, these costs will come down due to competition. Hetzner is a big provider which is famous for their network quality and cheap transfer. In addition to their pretty well designed self-serve cloud and dedicated server control systems.