I can't comment on the economics of it but amazon search is awful, and I think it's by design, not just by design though.

I was recently searching for some draw runners of a certain fixed size. Just cheap ones for some drawers I'm making for a workbench.

Found some cheap ones but not the correct length, but it made me realise something; If I sorted by price low to high the cheap ones did not show on any of the results pages. Amazon was purposefully showing me more expensive products.

I took some info from the cheap ones, searched for that, and the ones I wanted showed up in the search.

I wonder if anyone has trawled all of Amazon, and made a better search tool that doesn't try to rip anyone off?

Anyway, I am starting to find products cheaper outside of Amazon, including p&p.