What psychological tricks do retailers use to get people to spend more money?

An old couple used to live close to our home during my childhood. They used to make their living on their own by selling logs. They were famous in our area and were in good terms with all the customers. They were very knack at handling the customers. I closely observed and found a trick they were playing.

Customer: I want this log. How much is it ?

Old Man : It’s 160 rupees.

Customer: Can you give it for 140 rupees ?

Old Man: No, I can’t. It’s 160 rupees. We hardly get a profit of 10 Rs. selling a log.

Customer: I come here regularly. Please give me some discount.

Now the actual trick begins. The old woman enters the scene. She purposefully stayed away all this time.

Old Woman: What’s up?

Old Man: This customer wants to buy this log. I told him it costs 160 rupees and he is asking for 140 rupees.

Old Woman: There is no use of you. You don’t remember the things. The price of the logs on this side is 180 not 160. I told you 100s of times. It’s tough to live with you.

She then leaves the place. She didn’t say anything to the customer but the customer is now psychologically tricked to pay the full amount.

Customer (stops bargaining) : Can I buy it for 160 rupees ?

Old Man: hmm.. In business, sometimes you gain and sometimes you lose..It’s OK ..you can buy it for 160 rs.