Is it a scam for Liu to write on the spot?

This behavior is not a scam.

There is no deception in writing and painting on the spot. As for this street "auction" behavior, it is not a formal auction process of cultural relics and artworks. In essence, it is a hunger marketing method of selling and asking for prices, whether in the street or in the shopping mall. Commodity painting should adhere to the purpose of serving the people, not to engage in limited and exotic goods, but to clearly mark the price, childlike innocence.