"We'd like to sell you this book"
I explained that I couldn't possibly buy the book, as it was (to use a technical term) shagged.
"But it must be worth something"
"Not really madam, the book in good condition would sell for around £30 in the shop, but this one has half the pages detatched, and no spine. It would cost me £40 to repair."
"Well £30 would be ok, if thats all you can give for it."
"No madam, £30 is what i would sell it for myself, if it was all repaired and in good condition"
"This one isn't in good condition is it"
"No madam - that's why it would cost £40 to repair"
"Well £40 would be ok for it i suppose - you wouldn't go any higher"
"No madam, £40 is the repair cost - £30 the final value after repairs - I can't offer you anything"
"We could take the £30 for it"
"No if I paid you £30, then I would make a loss of £40 if i sold it after repairs"
"Well its no good making a loss is it ?"
A long pause followed. I could see the cogs gently clicking through the positions......Yes, she was working through the maths........ Nearly there - any moment now she will realise that the book is actually not an economically viable option for a bookseller.....
"I suppose we could take £20 for it if that is your best offer".