There are basically two cases. If you use Microsoft, you are often already paying for Entra ID and Intune, then still adding the Apple-side pieces for Mac support: Apple Business Manager and often Jamf or Kandji. If you do not use Microsoft, you are buying the full stack yourself: Okta or JumpCloud for identity, Jamf or Kandji for device management, and Apple Business Manager for enrollment. Apple Business Manager is free, but the rest is not, and the cost adds up fast.
This means that, in practice, a managed Mac can easily end up costing close to twice as much to support as a Windows device.
You think there’s a standard way to do that? Just install company portal? That worked in exactly 1/20 cases. It’s an exciting new error on every single device. Awful. Just awful.
But if you also wanted identity, there are plenty of free selfhostable SSO/ID providers out there. If you're just starting out and not at the scale where a big Microsoft CoPilotM365OfficeWhatever contract makes sense, you probably don't even really have a need for a lot of this stuff. A minimum contract for Jamf Pro is like $5k a year or something. That's two well kitted developer MacBook Pros per year in license costs.
Jamf will do that. Apple will not.
As far as identifying a bug in the software and getting it fixed, or requesting a feature, you run into a brick wall. Taking that feedback from customers is not the Apple way. This is why there is a market for third party MDM companies in the first place.