It makes sense for the service provider to discount a known customer. The service provider must ask himself how many potential customers he must talk to book one appointment. When taking the wasted time on talkers who do not follow through on appointments there is value to taking a booking from a known customer. But if a service provider is in such demand that he is constantly booked weeks or months in advance there may be little motivation to lower rates. But even then a service provider in high demand still has the cost of no shows so even then there is a value to a repeat customer. It usually all comes down to supply & demand.