Three for two

The bookshop has a three for two offer. I made some use of it today, by purchasing three copies of the same book. One of these I intend to keep and read myself, the others are for other people who also wanted a copy. I was mildly disappointed by the reaction of the bookseller - he just sold them to me like he would have sold me three books that weren't the same. Far too professional. I had hoped to have the opportunity to use some comedy lines. Something along the lines of:

"You do realise these three books are all the same, sir?"
"They are? How stupid of me!"

That kind of thing (booksellers are very polite in my head). Or maybe "Oh! I thought the offer meant that if you bought two of the same book then I got a third copy free. I hadn't realised I could have three different ones! I am so blonde."

But I was not offered the chance to say these things. I paid my money and left.