I am assuming that when you say "that you were told..." that you are referring to your company, that it wasn't the wholesaler who changed your price. I also assume that the $2,800 was a delivered price that included shipping.
I think the first thing that I would do is track down the tech that did the work and see if he really did all the work that was claimed. It may not matter but at least you would know what you were dealing with.
What if the customer was willing to buy it "as is" and go time & parts rather than maintenance contract? If my price was to be $4,200 less, that's the route I would go and take my chances. Your dealership has eliminated that possibility.
From a company perspective, we have always added reconditioning costs as well as "fluff" charges to equipment bought from a wholesaler because of the risk of the unknown that might not come to light until way down the road...hidden service problems from a lightening strike or bent frame, etc., inventory that never sells whatever. All that being said, there is no justification that I can think of for a 300% increase. I have to believe that if you told them that they are stuck with it at that price that they will reconsider. Our goal is that the sales cost needs to be 25% of the street price of new. That way Sales reps can sell at 100% markup and the customer is getting it for 50% of the cost of new.