I just think stacks of 1 are just a waste of time. In the time it takes to sell 50 stacks of 1 I can sell 2 stacks of 20 and make more.
It might just be a low level market thing, but I list larger stacks of 10 and 25 right beside a bunch of one unit stacks, and find that the single items sell and the larger stacks just sit there for two days. I suspect that many first-time players, like myself, just can't afford a stack of 25 green goo (or other early supplies), but are happy to purchase the few that they need right here and now. I guess that by the time you're level 50, most people have enough credits to just snag a stack of 99 units without even thinking twice about the price, and I very much look forward to being able to gather up things that I don't have to break into a dozen stacks of one every morning. Some day, soon I hope!