Does the coming out of barbers to the Grand Mosque courtyard to receive pilgrims and bring them to their shops constitute "talakkī al-rukbān" (meeting travelers before they reach the city to buy their goods)?

The prohibition of intercepting riders (rukban) is to ensure that sellers coming from outside the city are not exploited. Intercepting them before they reach the market and become aware of its prices often leads to purchasing their goods at lower prices.

"Rukban" here refers to those arriving from a journey with goods to sell. They are entitled to the option of rescission due to exploitation (khiyar al-ghabn) if someone intercepts them outside the market and buys from them or sells to them something, and they are exploited in a manner that is unusual.

As for intercepting someone who intends to perform halq (shaving the head) or taqseer (shortening the hair) near the Haram, this does not fall under that prohibition. This is because there is no exploitation involved; the price of shaving is known, and no contract is concluded at the time of the encounter. Rather, it falls under the category of brokerage and guidance, which is permissible.