Do airports have anything in the nature of a street library?
Airports are one of the most commercially profit driven spaces in the world. Literally every aspect of an airport tends to be directed towards extraction of the maximum amount of money possible from those who pass through it.
This is an inevitable consequence of a number of facts that combine to make a "perfect storm" of profit motivated management - airports are frequented by people who have no option other than to wait around and who are self selected as people who can afford airline tickets (and therefore have disposable income, far in excess of the general population); And they are frequently highly deregulated commercial spaces that have separate laws from the surrounding jurisdiction(s) which are designed for security and aviation safety reasons, and which pay little attention to consumer protection - after all, there's no permanent population of people who will complain about being exploited.
Commercial rents are high, because businesses are lining up to get access to these cashed-up bored people; And so prices are high to cover these enormous rents.
This leads to nothing being provided free of charge (other than to people who have paid through the nose in advance for access to business class or frequent flier lounges), and to a ruthless expunging of any unlicensed, unauthorised, or citizen initiated activities that could, even hypothetically, impact the profitability of the paying tenants.
TL;DR - if you tried to set up a street library in an airport, the franchise holder who paid an exorbitant rent for the right to operate the airport bookshop would have you arrested and dragged away in chains before you could say "community spirit".
Buying a book (or literally anything else*) at an airport is a last resort; It will almost always cost more than the same book bought in the city centre.
Airports are a microcosm of the corporate state fantasy, with lots of wealthy people being fleeced by unscrupulous big business operators in an environment where security is intense and no disruption or dissent of any kind is tolerated. The only reason they work is that nobody lives there.
*The exception being Duty Free purchases when flying internationally; And even then, caveat emptor. In theory, buying duty free is cheaper, because you split with the retailer the difference between the normal retail price and the price without the local duties and taxes front which such exports are exempt. In practice, many duty free stores in airports will mark up the prices, so the split is almost entirely in their favour, and the benefit to the buyer is minimal. The trick with duty free is to have a good grasp of the regular price you'll pay elsewhere, so you can spot the difference between a genuine bargain, and something you'd be just as well off buying elsewhere (and saving the hassle of lugging it with you on the plane).