Wanna upgrade my bike to carbon,and find this rim http://www.carbonbikeoem.com/bike-rims/mtb cost only $169,so is this a real carbon?and what is the general price of carbon rims?
I would be very careful with a deal that sounds too good to be true. Take a look at what happend to this carbon wheel in another question: Carbon Wheel Heat Bending
I wouldn't buy from a company I've never heard of before and will never hear from again (like when the wheel deforms from the heat of braking and I'm trying to get a refund). Even the tagline on that website ("Welcome to carbonbikeoem.com , enjoy the great savings now!") is a red flag to me. It suggests that the only point of their products is that they're cheap. The generally poor grammar of that website also suggests that it's not a serious company, but just someone who can cheaply produce things from something resembling carbon fiber.
It would be much better to get a decent set of aluminum wheels, then you don't have to worry about how long they last before they snap. For $85, you can get a Mavic XC 717 Disc rim that weighs 395 grams. Mavic is a well-known manufacturer and you are guaranteed that this is a good product. It weighs 35 grams more than those carbon rims. Who cares about 35 grams ?