f1 f2 and k7 are cheapest, a reasonable f1 or k6 would probably be best money wise and would make the best daily rider,
k0,s are the ones that kicked it all off and are sought after worldwide hence the prices
As trigger says k2,s are really good , not quite as desirable as k1 or k0, but they are starting to fetch big money as well, as for relability they are all good, the ones that are the biggest ppain in the butt are k7 and f2 with there bloody lean burn pd carbs, f2 being the fastest sohc750, k7 having the best refined engine
so there you have it
pete