They pay for the scraps they receive without a choice.
They pay for the costs of maintenance.
They pay the devaluation of money while it is sitting in an order (time-value-money).
They can't afford to lease out planes based on your model.
They would never get to a point where they could accept larger requests worth billions, because they can't even keep up with the growth of 1 single airline. (the profit % and $ are way low)
They would have cash flow problems, as in they have asset, but not cash (because the cash is either tied up with orders, unsold planes, or leased out planes)