You don't always have to sell in bulk. Sometimes your stuff moves faster if you split quantities.

The other day I bought HQ food for a CUL quest. There were a bunch of x99, but a fair number of 3-packs. I bought a 3-pack, turned 1 in, and sold the other 2 separately slightly increasing the unit price. They were both sold within a day. Figured they would since it's a quest turn-in.