Clean tidy and good runner I think it would get money even with springer heads. you couldn't rebuild one without throwing a few grand at the problem.
God knows what full rebuild on a bevel twin costs these days, it used to be 5 grand on a good day years ago.
But you are right desmo has a premium.
I used to feel sorry for the guys when I would quote that figure but that is what it could easily cost. An 860 with rooted heads and other problems was closer to six grand. When you did the maths on the cost of the mandatory big end assembly and more often than not a gearbox you were well on your way.
Throw in bearings, pistons, valves, seats, guides etc etc the whole thing could get quite scary and given that I am about to start doing some old Duke rebuilds for a couple of guys I did engines for years ago the scary factor will re-emerge!
The big secret with the older roller bearing big end engines and all of the older bevels for that matter is use quality oil and change it often - oil is relatively cheap compared to rebuilds !!! If you buy oil for your old Ducati the smallest container should be 20L, lol. Then you have no excuse.
As far as the Desmo versus springer heads go many racers are of the belief that well sorted spring heads perform EXTREMELY well. The Desmo's advantage is high revs due to control of valve float but half the time the Duke will lose a big end or timing side main bearing before valve bounce becomes a problem.
Dave Mac