Reality check
1) every section in a supply chain has to make a profit other wise it collapses and the items not longer become available
2) the cost to profit ratio on replacement parts is massive so replacement parts will always be a lot more expensive than the cost of making them.
Perfect example is a $ 1.50 rectifier for one of my BSA motorcycles made in 1954 , sitting in a Lucas warehouse till 1984 when it closed down had incurred $ 1,332 in warehousing costs over that period of time and then there is a $ 4.50 picking fee, a $ 2.00 invoicing cost + warehouse profit of 15 % added to that, transport costs and retailer profit .
The aftermarket ones that are hand made in Indonesia are $ 45 made on demand so they take 3 to 6 months to be made.
3) most factories only sell in wholesale quantities which could be from a box of 20 to a pallet of 2000 and the lower the profit margin is the larger the minimum purchase quantity .
4) the Greedy Amazon effect is preventing companies carrying your parts because the fast moving parts get sold through Amazon which leaves large warehouses full of very slow moving parts on which there will not be enough total income so the warehouse closes and your only option becomes replacing the entire engine
