I know, as someone who has worked in the cycle industry and as a customer that if you can't supply the goods the customer will go elsewhere, and elsewhere these days can be anywhere in the world. When I left school I worked as a bicycle mechanic for the biggest bike shop in town. I also had a Freewheel mail order catalogue and a lot of the parts that they had on sale I couldn't get from my boss who would want to sell me an alternative that I didn't want. So, I went to the competition where I didn't get a staff discount but I got what I wanted.
The point is, that if, as a dealer you can't always make a profit or buy at trade prices then sometimes it makes sense to sell at cost price or even at a loss to ensure future business from the customer, and the chances are, that if you are selling an expensive quality part at a good price, with a smile, the customer will come back again and again.