Perhaps. But, even small screws are a part of their requisitioned inventory as they would naturally need to be for manufacturing, all with their own packaging and SKUs for after-care/warranty. These need to be QC'd as consistent in form factor not just from batch to batch, but year to year.
They aren't merely resellers or drop-shippers of a raw product. They're supporting these minor parts as official products and carry the burden of the implied liability that comes with them ; I/E guaranteed fitments, performance and fiscal and legal responsibility if these tiny parts cause other failures - failures that may equate thousands of dollars in damage or adjacent harm to other parts or people.
Costs to support them in this manner are different than a mass-production in bulk for general construction in boxes at a hardware store where QC is less critical and responsibility for application is zero.
This doesn't justify the exponential prices often seen. But, it's helpful because it's still not really an apple to apples comparison.