balanced crank? dax sells em custom made from a mould for $60... porting? Arrow sells pre-ported jugs for $60. Mikuni carb? sells for $100. no exhaust? thats the biggest power maker! chrome covers? $35, but useless, chuck em. High compression head? $90, stock head can be lapped, chuck it. Reeds? $65 Maybe internals like a better piston? ehh, only $40 for a 70cc. So thats a value of $595 tops for $660. Not bad if you think of it that way... until you see the savings when you do it yourself...
Port yourself: $535
Lap the head down 1mm or so: $445. Cooling gains are negligible (if you really want a better head, go with the Puch 70cc hi or hi hi for $40)
balance the crank yourself: $385 + $10 for JB weld filler so $395
ditch the chrome covers: $360
stock piston is fine: $320.
Ditch the reeds, they're too small to see gains from the 18mm mikuni: $255.
use Arrow reeds instead: $320
build your own damn exhaust: $345
Power output: varies depending on power range
Pride: through the roof
Sorry any vendors that may be offended by this: I know you're trying to make money and your products have their places (well... most do) and if you sell lots, great. But prebuilt motors for such high prices I simply do not understand. If dax can custom pour and drill a crank and sell the whole bottom end with it for $60, I dont see any reason why I'm paying $80 for a "tuned pipe" or $90 to even a whopping $180 for a "better" head.