Custom made cable is indeed cheaper. The quality depends on soldering skill of the technician. Personally, I would go for originally cable packing if it is higher-end cable like "diamondback". The reason being high-end cable comes with more sophisticated shielding techniques and requires delicate skill to solder the conduit to the plugs. Quality of cable will deteriorate if it is not properly handled.

I just bought a pair of "diamondback" RCA cables to connect my CD player to amp. The sound is really clear and clean.