They were expensive even then, the Brown family brothers were their patrons. The Brown's were merchants in Newport and among other business ventures had an exclusive franchise from the british govt. to make candles. The Brown brothers were VERY competitive about EVERYTHING, including who had the best furniture! As is usually the case, it takes a bunch of different circumstances that come together at the right time & right place for a masterpiece to be created.
The desk that sold for 12 mil was the only one of 10 known that was in private hands. It was sold by a Brown family member to fund a restoration project in Newport. That desk had been in the family mansion from the time it was built and delivered by goddard/townsend in 1760 to when it was sold in 1989, it went to a good cause.
You can buy a line by line hand made copy of this desk for about 50k, the Brown family were the first customers that had one built to be placed where the original had stood in their house for over 250 years.