They do seem very variable - there's one on ebay as a classified ad for over £5,000 but that's daft. I'm not in a rush but may end up buying the component bike & engine separately. There are people who produce the appropriate engine plates. Or of course, being fickle, may have my attention directed elsewhere. Not a thumper of course so purists look away.....
When I rode in the Midlands Classic Club trials someone had one and I always liked the look & sound of it. Another bloke actually used an almost standard 3TA and he ran rings round me - but then so did almost everyone.