Yea, they consolidated One and Pro a little ways back.
We are on the $20/Per Month for 100 PC. If you break it down that's $0.20 per PC for the month. We don't normally break the 100 PC limit although we are planning on moving up to the next tier at some point this year.
If you do happen to go over the limit by a few PCs they don't say anything unless you do it every month, then they want you to move up. We usually get around it by only using the free Ninite.com stuff on random PCs that we take a look at that just need Java updated or the user wants Spotify installed.
We generally reserve the Pro stuff for our MSP clients and PCs on our tech bench who are paying for Cleanup/Updates.
Probably one of the best reasons we do continue to pay for it is that we can automate it with our HelpDesk and NOC people and our MSP clients get updated everyday without me ever having to lift a finger.