I was approached to buy a book on the Forbidden City in Beijing near the entry for 60Yuan, saying that it costs a lot more in the bookshop. I later found that the book cost the same inside.

Also, try to go there early if you are visiting the Forbidden City, since a lot of sights start to close near 5pm.

But I guess such minor incidents tend to leave a bad impression, on otherwise very nice and friendly, possibly honest ones I met.