So, okay, that's the story: working bigger isn't always proportionally slower or more difficult than working smaller, across reasonably moderate changes in scale. 12"x12" isn't 4x the work of 6"x6".
Put yourself in a buyer's position, wanting to buy a piece. How do you budget in your mind the thing that 12"x12" vs. 6"x6"? Probably not as "oh those should cost essentially the same".
One looks like a window hanging, one looks like a tree ornament. Prices presumed to correspond.