It defies belief what some items fetch on e-bay. My concern is that the average Joe in the street will see that as the current going rate when in fact it is just what a person was prepared to pay on that day. I sold a "C" RFM for nearly a quarter that price a couple of years ago after I paid less than what you offered for a good Series B item. At the time I was just happy to have minimised my outlay on the B item. I always thought the UFM/headstock was worth more than an RFM so maybe there has been a shift in values or, more likely, this was a desperate man who wanted this RFM, come hell or high water.
It does not augur well for those trying to get their basket case back on the road. Be prepared to see more Comets broken up for their parts or a substantial rise in the price of scruffy ones. £5,000 for the bare bones of UFM,RFM & forks means that once you add engine (£3,000), gearbox (£300), Miller parts (up to £1,000), wheels & brakes etc. etc. you will have a bill for £12,000 +.