Base Unit vs. Unit

I set up a product catalog, where I created the Base Unit (Bottle) and
one additional unit, called Box (6 bottles equal 1 box).

When I use my product at quote level (existing products) and want to
select the unit of measure, I can select only the base unit.

I thought I specify the price based on the base unit at pricelist
level, but during product usage at quote level, I can choose using
base unit or other unit.

Thanks, Mikl=F3s