The bicycle building business is more of light manufacturing and motorcycle building business is more heavy manufacturing. The difference is at the component level economics. Bicycle manufacturers buy the same Shimano groupsets as the local bike shop. Motorcycle components are mostly bespoke and manufactured to a specific motorcycle manufacturer's specific specification.

So motorcycle components don't have all the overhead costs of bicycle components. There's a lot of marketing costs in the price of a Shimano groupset whether it arrives at Trek's loading dock or via Fedex at a neighborhood bike shop. The chain and gears on a Honda CB650 didn't have a marketing budget to build brand awareness.