I find it hard to compare prices/V.F.M between different brands without knowing the quantity.
Take this page for instant:
http://www.opieoils.co.uk/c-785-20w-50.aspx
Looking for boxer engine oil I can presume roughly which are the small Vs big bottles, as the prices jumps considerable, but I do not know if, let's say, I'm getting 4 or 5 litres in the large bottles without clicking into the separate items, one by one.
In a sentence: have quantities listed along side the pricing without the need to look at each item.
Apologies if I'm missing a "compare items" feature.