I would argue there is a lot that goes into the proce difference. But one of the biggest things that many overlook is the scale of production. There are many more motorcycle produced than bicycles which means the parts production is optimized well beyond that the bicycle market will ever be, especially with all the marginal improvements being constantly made on the bicycle side of the equation. I could go on but I'll spare you all that boring reading
willingness to pay is how things are priced.