You gotta remember that quantity has a lot to do with it too. The Car industry builds a LOT more of the same thing over and over again and even when they do modify things a bit the process and tooling is still very similar. This quickly leads to a significant cost reduction.

That said, if you buy a part at an automotive supply house versus going to the automotive dealer, you'll find increases that are similar with going from Hobie to the industrial wire company.

There is also a factor that most manufacturers (car makers included) plan on making a significant margin on spare parts. When you buy a car, boat, or piece of machinery, how many times do you ask to see a price list for common wear items and consider that with the overall price? Not very often. When manufacturers start trying to be more competative with their up front pricing the spare parts become a more important money maker.