Like most say, after the exhaust, aluminum subframe it gets expensive.
Carb tank about $600, carb wheels new are nearly $2k
After improving your riding, going on a diet, and adjusting your suspension you'll be much happier and richer!
After getting my busa and redoing the stock suspension settings you'll notice a huge diff, really do they hire monkeys to put these together out of the box?
Mine was so far off I wanted to cage the monkey that put mine together.
Theres a great walk thru on another busa forum, I'm sure theres one here too.
My mushy busa corners were solved by making the Laden Sag in the front as close to 3.449" as possible and then go wtih 4 clicks damp, 3 rebound
For the rear compress the spring two full turns or about 4mm and damp 7 clicks rebound 10
I'm 5'9 and 165 these worked perfectly for me heavier riders will have to play with them a bit and super bumpy roads will not be so forgiving, this also does NOT count if you've installed dog bones, extended swing arm, etc, THEY ARE FOR STOCK busas and for a good starting reference point.
OBTW you DONT need a special tool for the rear compression adjustment like the book says, just knock the top lock nut loose with an old screwdriver and hammer but dont be a gorilla about it!
Always remember to track your adjustments, and when I refer to clicks its from a complete IN position going OUT.