It’s another league, but I don’t get the point of mixing enterprise rack-mounts with Raspberry Pis.
VMs can add a lot of complexity that you don't really need or want to manage.
And (perhaps unadmitted) lots of people bought Pis and then searched for use cases for them.
One advantage over the used market is that you can easily keep getting the exact same one over and over again.
Not really, no. Not if all you need is "a computer". They're more interesting if you want a cheap ARM computer, or a tiny computer, or a server that sips power. Although for that last one they're also kind of dubious. If you can somehow get away with running what you need off a phone, that's way better value.
The Dell is essentially the main machine that runs everything we actually use - the other hardware is either used as redundancy or for experiments (or both). I got the Pi from a work thing and this has been a fun use case. Not that I necessarily recommend it...