It all comes down to the total price and doesn't matter how it's broken down as has been mentioned. As an RV dealer for many years, long ago,I am sure I know the reason for this. We had a dealer near the factory that considered prep As driving It onto his lot and putting a key tag on the keys. He priced rock bottom and they drove away. On the other hand we spent a full day properly prepping the unit. The prep sheet was a legal sized form in small print. It included filling LP, sanitizing water, trimming antennas properly, cleaning all construction debris, operating everything, leak checking and performing numerous adjustments and repairs. Everything was filled to check all gauges Including fuel supplies and waste tanks. And about a hundred other items. We priced it complete and ready to use after spending a couple of additional hours demonstrating everything to the customer.
Then, here comes the other dealers customer that sold at cost with a list of "repairs" that were prep items and expected it for free as "warranty." And in many cases the customer just did not know how to operate, but expected to pay nothing for hours of service caused by the selling dealer's poor methods. And, we were educated on how expensive and inconvenient it would be to return to the selling dealer. Unfortunately many try to compare to an automobile purchase which is extremely naive at best.
If someone maintained that they were qualified to do their own set up and prep, we would order a coach for them without charging the set up, priced accordingly, and they were provided with the extremely detailed copy of our prep form for their use which they signed as their responsibility. But, sorry, you can't have it both ways. I am still dismayed about how many *******, problems, and complaints on this forum are directly attributable to original prep and setup.