What's a fair cost for setting up my TV for towing?

We bought our trailer new last year. We had the hitch, electrics, sway bars included in the price. We also had them install (weld) on a receiver/hitch and electrics on the back of the trailer so we can pull the boat also, dealers expense. We are guessing there was at least a thousand or more in work. We negotiated a price and after that was agreed we said it was to include all of the above, dealer agreed to new terms.