there was no Dust before Patch 3.0, so if you wanted an Item, you had to farm until it dropped.
after Patch 3.0, Dust was introduced, so players now have the option to farm for an Item or spend Dust to get it right away. Farming for an Item requires lots of time based on how evil the Random Number Generator is feeling versus using Dust which requires lots of Gold & Legend+ Items dropping to convert into dust.
this is a story I wrote after spending lots of Gold to get Dust after Patch 3.0 came out.