most would argue that the official cable IS cheap (only the cost of 2 or 3 scans at a main dealer) and as it's the only one with the R&D backing so you know it's not going to sent 12V to the wrong thing and fry some circuitry in your car.
plus when you come to sell it on it'll cling to it's value, whereas a cheap cable won't. so in the long run it won't cost you much more, and will be less troublesome.
