Have you ever tried to buy in guild stores something cheap - Ta or garlic or something similar? When I need to check a few cities to find best deal for sharpened weapon or jewelry, it is more or less OK. But to spend half an hour looking for 100G purchase - not fun and not really lore friendly. As a buyer I would really like to have a corner store where I can go and buy cheap stuff.
As a seller (and I am in 4 trade guilds), I never sell any cheap things - they are not fast to sell, and I better use my slots for something at least couple thousands.
Possible solution - add to capitals general stores where anyone can list some positions, but only cheap one - let say less than 250G or even 100G. It will not affect current markets, but will add convenience to deal with really cheap stuff - food/entry level gear/green tempers/so on.
1T brought quite a few new casual to the game, such stores would be very beneficial for them - it can be hard for a newbie to keep up with weekly requirements in the active trade guilds, and there is no any sense to try to sell in small guilds. Ability to dump cheap mats/gear would be very helpful for them.