...is there $70,000 more car in the porsche then in the kia?..probably not.
Maybe, maybe not. But I can look at a Porsche and a Kia next to each other and easily see huge cost differences. On the other hand, while one can (sometimes) see cost differences with wire, for me it is hard to understand the huge differences in cost. And there certainly doesn't seem there would be the overhead in cable as in other aspects of audio and warranty work would seem to be lower and easier.
As for percentages of mark up, some of these cables must be far above the 100% - 200% range listed above.