Today CCP Punkturis tweeted this interesting picture. A feature like this has been proposed by the player base numerous times, as mostly ratting but also pvp loot can stockpile over players heads quite fast. So fast that bulk-buying and selling them can get a profitable business itself.
When this feature finally gets implemented (maybe already in Phoebe?) it will likely also make traders happy as uncareful multi-sellers may sell their shiny mods to an underpriced buy order.
-AkaAlias
