yeah, i've gotten those karts for around $150-200 each.
why not build a couple? search the forums and the web for karts that really appeal to you that are within your skill level to build, save money and have fun building! find $99 coupons for the 212cc motors from harbor freight (i think they're on sale for $109 till the end of the month). if the karts are for little kids then you can build them light and use centrifugal clutches (about $30, save money!). if the big kids (including yourself, lol) want to ride them, then get TAV2 torque converters (about $130, but way better, beefier and more durable than centrifugal clutches).