Ah, thanks. So the answer is that it's not sustainable. Got it.
Yes?
That's why it's being usually run by tax money. A regular flow of funds. Something you can plan and work with.
As long as their costs are less than $5M per year, they can effectively run forever, barring any long-lasting financial depressions (the likes of which we've never seen), or severe financial mismanagement.
This is how many museums and universities operate, and what the above commenter was referring to. :)
Here is the relevant part again:
> because its revenue from goods and services is less money than it spends