The last time I checked, CarProof doesn't really allow for an option to Subscribe for unlimited monthly checks.
You pay for each and every VIN you run. This was true for Dealers as well, and I'm sure it hasn't changed.
(Dealers probably got a discount, but it was still per VIN they run).
Autocheck and Carfax both have unlimited options for consumers, so I'm sure they have dealer options as well.
If you are shopping around, get an unlimited Carfax account for the month. If you are serious about a car, get the Carproof just before you buy.
I've had Carfax come up with a clean list, and Carproof showing an $8000 accident report.