Sorry. How much is a book?

I would do this to incentivize shoppers to take as many as possible. Like at a charity shop that needs to make room for a sizable donation or just to churn the shelves a little.

The sign is still pretty amusing tho.

This was outside a charity shop. 👍
100 old karens with nothing to do must have argued that they are entitled to one book for .50
- 100 old Karens agree: "We'd like to speak to the manager."
We do an annual charity book collection and we do this towards the end of the day too. We really don’t want any books left if we can avoid it.

This is one of those times where seeing it all written out feels redundant, but you know if those examples weren't there people would be asking if one book cost £0.5.

That would be me

I’m sure they had to do this because they had too many people asking “how much for 3 books”.

That or just because funny.

Used books are hard to move. This is one reason why most libraries don't take donations. These sales are for clearing shelves more than for making profit.

Not hard to move. Almost impossible to move. In my shelf apart from some old leather bound books from my grandfather (Churchils world history, complete Hamsund) and CE and hard cover 40k books I have nothing but paper trash
- People need to internalize this. Generally speaking, nobody who has a choice wants our old crap.
A library I used to use would put old books for sale outside. If someone came in to pay for them, great, but if they happened to mysteriously disappear, that was fine too.
Speaking for myself, I'm too paranoid to buy a used book from some random charity because I can't trust they ensure the books are clean before selling them.
My family brought home a bundle of music books from some charity event when I was a kid, and it unleashed an infestation of silverfish that proved impossible to get rid of. It's been more than twenty years and they still pop up on my parent's walls every few months.
Edit: to be clear, I'm not blaming the charities for this. Some people use donation bins as an excuse to offload literal biohazards - just ask a Goodwill volunteer how often they receive soiled clothing. Books are simply harder to check than many other goods due to the literal hundreds of hiding spots between the pages and in the bindings.