You don’t have the time to carefully price things out at the moment in EVE Online. You need a whole pile of items right now, and money isn’t an object. So wouldn’t you rather just buy in bulk and sort out the details later? Then the upcoming multibuy option is for you, a chance to just buy stuff in bulk without spending too much effort on pricing out individual items.
There are downsides to the option, of course; rather than buying the items at the cheapest possible price, you’ll buy the items at whatever price allows you to buy the desired items in the wanted quantity. You can read all of the details in the most recent development blog on the new system; it’s meant for players who are more concerned with getting items quickly rather than playing the market at a particular moment.