Slots

5-20$ 5-15$ - SKETCH and flat color both slots
25-40$ 20-35$ - SKETCH and full color
45-95$ 40-70$ - Line with color and simple shadows both slots
>100$ >75$ - Full color both slots

The above rates are summed up with two slots at once. Therefore, even if one slot will be 10, and the other - 90, will still be full of art.