User blog comment:Care Level/On Anti-Snowball, 2v1, Melee v. Ranged, and player satisfaction./@comment-5035765-20140709044939/@comment-5331854-20140710095757

There are two price-classes for items: 40% Selling Value (Doran/Prospector/Consumables/Gold Income/Guardian Angel) and 70% Selling Value (everything else).

Having those as 40% Selling Values gives them lesser overall value in ideal situations while being still great for those moments of getting snowballed. You could still reset the stacks by rebuying, but you could also have gotten a Pickaxe or B.F.S. for the gold you've just throwed out of the window.