When there's items in your base inventory, you can add to trade bay to have a little value picker dialog.
Sometimes the values in that picker dialog are actually the values you buy/sell buymax/sellmax/makemax values you set already, so you can adjust them on the fly. Sometimes they are random values that seem based on /mc.
Just small feedback if they can always be pre-filled with the values set for that item if possible.
I have a hunch if you docked in the base, and opened the "Modify" dialog whilst in the tradebay it "caches" the prices, so the "Add to tradebay" values are referencing them then. But not 100% sure why sometimes the values are prefilled correctly.