The broker that Aruita mentioned is the same one Patricia friend used. So, no back door there.
There is however what's called "Chocolate plates" which is the back door. It can be a real headache for the uninformed.
The difference in the price could have something to do with age, and type of vehicle. But, that's a guess on my part.
But, from many of the posts I have read from people currently in the process, the price appears to be running higher then 1,500 and closer to the 2K-2.5k figure, as well as a longer process time...but you won't know until you get into it.
Delays make sense seeing how there are a few thousand ex-pats who live in Q.Roo alone who are caught with foreign plated vehicle that they want to nationalize.
I personally would always want my lawyer involved to ensure that I am dealing with the right person, doing the right thing on my behalf.