I'm an electric guy but from my understanding of gas carts it could be lots of things from a cable adjustment to a clutch assbly to a rear axle and you won't be able to tell how the motor runs until it's under load.
So, can it be expensive? I would say depends on what your paying for the cart and what you call expensive.
Budget the worst case scenario, say about $2000 and add that to the price of the cart, is it worth it if it costs that much?