For a small startup, possibly. As you grow, like many things, it doesn't really scale well once you have to start paying people full-time to manage the whole process.
You can save yourself heaps of money by buying used Macbooks off of e-bay for a startup, but it becomes a nightmare at scale when you get an IT department that needs to manage it all with uniform security updates, and lifecycles.
I doubt they'll ship you pre-MDMed devices from the refurb store, but you should still be able to add them to your account manually:
For companies, there's a lot to be said for standardization though, for my last job, I just used my own phones and computer gear anyway so it was what I wanted and I controlled it (other than MDM latterly on the phone).
Buying isn't that hard.