Books are a luxury. Mortgage, food, bills, clothes, water, heating and children are non negotiable. Buying a book is.
Yes, indeed, agree. But I said "luxury-priced".
75p or £1 to order a book from the library is still a bargain. Libraries are indeed a whole other thread, but again, soon we'll have no more libraries if the government gets its way. Their funding for the actual books portion of the service is shockingly low. Librarians are up in arms about this. But realistically what can they do - people don't borrow books if they can buy them for £0.01 + 99p postage on Amazon and without footfall and user statistics they can't argue they're essential unless they diversify into other "services" and so their core funding for books falls again, just to stay open for those people who genuinely can't afford to read a book at all unless it's free.
If you read a lot, I agree that the price of a paperback at £7.99 seems high if you are buying one a week for everyone in your family. But you can borrow up to 6 at a time from the library, and when you do want to buy the newest bestseller you can then afford to pay more for it from somewhere that isn't Amazon.
It is a choice, in the end - just as eating less meat in order to buy free-range. If you have the choice to pay for meat, you have the choice to pay a bit more for higher welfare meat and eat it less frequently, and eat more vegetarian meals instead. If you have the choice to pay for books, you have the choice to pay a bit more for them from a better retailer than Amazon and borrow more free books from the library instead. Some people have no choice but to eat vegetarian the whole time or only borrow books from the library. For some people it is tougher than others. But if you are a big consumer of something - books and reading - for your leisure and pleasure, then perhaps you should consider supporting the industry that makes it possible? Same for avoiding pirated/illegally streamed films and TV vs seeing them in the cinema etc.
Bookshops are trying to adapt their model, but the industry is extremely hard for everyone involved in it from the authors onwards (most of whom are paid less than a minimum living wage per year from their writing). Movies and TV make money from advertising as well as box office/ratings. Books don't.
Again, like I say, it is difficult to avoid the temptation of super-cheap on Amazon and I do sympathise. But they are terrifically bad for the book business in a lot of ways and if the diversity of the retailers we still have is lost then they will have no need to sell cheap books any more. They don't care about readers, they care about revenue. And their income stream is now so diversified that books are a very small part of their income stream. They can decide to charge what they like for books if nowhere else is holding them to account at all on the high street.