Its really not cheaper. Keep in mind that if you go 520, you will have to change both sprockets due to the stock sprocket teeth are thicker and wont be able to house the narrow 520 chain520 is lighter chain and narrower. less weight, less rotating mass, bike should run quicker, maybe not that you could tell its quicker, but it is. if your gearing is 17 front(has 17 teeth on it) and 44 back(dont know stock gearing) if u change to a 16 front you will gain some in acceleration but lose some top end mph. 1 tooth difference is front is equivilent to 3 in back. 16,44 would be same as 17/47. one down is front is same as up 3 in back. reverse it for more top end, 18,44 is same as 17, 41. normally is easier and cheaper to replace front sprocket( 20 bucks to 40-50 bucks for rear) hope this helps and diesnt confuse u.
Listen to Nuk Boy. Don't screw around with the 1000cc monster it will bite you in the ass if you start changing crap that doesn't meet specifications, just so you can be a part of the crowd at the coffee cafe.I would not recommend a 520 conversion untill you are very comfortable with the bike as it is. You will get lots more torque on the rear which will increase your lowside, highside, and tankslapper risks.
What I have done that works for me is:
RK VRX Chain(The only 520 with high enough tensil strength for the 1000)
Sprocket Specialist Titan aluminum sprocket.
45 teeth rear and make sure you keep a steel front sprocket.
It's the same set up as Matt Mladin.
By the way.... The 1000 eats parts for breakfast. So if your going to go 520. Plan on replacing chain and sprockets as often as your tires.