I can't even count the number of times I have searched for Product-X, by lowest price, and encountered a dozen pages of Clearly-Not-X and Actually-Just-An-Accessory-For-X before even reaching the first X.
Or Item-Sold-By-Weight-Y, that comes in 30 different package sizes, none of which is tagged with comparable unit prices. If you want some Y, you cannot order your search by $/kg or $/L. And sometimes it's difficult to figure out exactly how much Y you would be getting. The giant barrel of industrial generic will be listed next to the 20 oz bottle of gold-plated spiritual-grade Woo-Woo brand.