Perhaps the idea is that the production becomes automated - the "builders" (us) usually will have converted everything to stite and energy by the 12th month.
The ship returns and we return to our home planets, leaving the automated mules producing stite and erergy to be checked periodically by maintenance crews.
As operation is automated - no food required and therefore reduced price.
Of course, if colony ship returns with colonists...then price should reflect the increased demand of more mouths to feed.