Cables make a difference in sound in my experience, to the point that they can make or break your setup. Cables can either throttle or unlock the SQ of your system.
You can be perfectly happy with the sound of your system, not knowing that the SQ is being held back severely by a certain cable. And you can't know that until you try a different cable in your system. When you do, there will certainly be a change in sound but whether that change is for the better, for the worse, or sideways depends on the individual listener. If it's for the better, then it's up to the system owner to decide if the price delta is worth paying.
If you hear no difference when you change a cable, most likely your gear just isn't resolving enough. Then you're better off spending on better gear than on more expensive cables.