It's assuming the fixed costs can be recuperated... if a firm can exit the industry and sell its initial investment at a comparable price to what they bought it for
That sounds like assuming no depreciation and no cost of capital, right?
Otherwise, imagine a firm considers increasing its capacity via investing in a productive asset, for an upfront cost A. There is a depreciation rate d, and a cost of capital (interest, dividends etc) of c. If the firm sells the asset after r years, then its sale value in year r will be something like A x (1 - d)^r, and the present terminal value will be something like A x ((1 -d)/(1+c))^r.
So in the business pan, the firm should assume a fixed cost not strictly of A, but rather of A x (1 - ((1-d)/(1+c))^r). If (d+c)r is roughly 1 or more then this will be about A; only if (d+c)r is much less than 1 can this cost be ignored.
As | understand it, it assumes no or low depreciation, but says nothing about the cost of capital. The definition of "profit" that I've been using is "extra profit to the company after all investors have been paid at the rate the market would demand, and employee and entrepreneurs have been reimbursed for their time and effort".
Example nicked from this online Berkeley lecture.
Monopolies are bad (morality and economics agree here).
Firms that pollute are bad (morality and economics agree here).
What about monopolies that pollute?
What about strong monopolies that pollute and receive government subsidies?
Well...
Pollution, and other negative externalities, cause firms to produce too much of their product. That's because they don't pay the full cost of the product, including the impact of pollution.
The equilibrium behaviour for monopolies is to produce too little of their product, to keep prices and profits high.
So a monopoly that pollutes is subject to two opposite tendencies: the unpriced-pollution tendency to produce too much, and the monopolistic tendency to produce too little. If the effects are of comparable magnitude, then the monopoly might be much closer to social optimum than a free market would be (the social optimum, incidentally, will generally involve some pollution: we need to accept some pollution in the production of fertiliser, for instance, in order to have enough food to stop people starving).
In fact, if the monopolistic effect is too strong, then the firm may under-produce, even taken the pollution effect into account. In that case, we can approach closer to the social optimum by... subsidising the polluting monopoly to produce more!!
And that, my friends, is why economics is not a morality tale.