I am a big supporter of this idea Raithlian.
It has been suggested by numerous people repeatedly, including myself.
When a buyer goes to the gem store in Stronhad for example, he/she can press ctrl and click in order to enter the number of gems that he/she wants to buy. I fail to see why such an approach can not be implemented in the auction house setting as well.
More often than not, I am looking to buy a single item in order to make a stone and the seller, who is likely afk, is selling a huge stack that I have absolutely no use for.
Perhaps, lack of implementation is due to the fact that people do not want to allow partial sales of certain items such as trophies (and goods that are being sold in bulk). Perhaps, accomodating these people would make the implementation of this idea too complicated.
If this is indeed the case, I would support a patch where everything can be bought in partial stack form (even trophies). But perhaps other people would disagree with this sentiment.
I am just tired of the following two choices:
(1) Buy the entire stack
(2) Go without
And I usually end up going without.
