When the client ask you for cheap price, you can go up to 30$ less than the price you gave him for services 150$ and plus in respecting some situations (you can always reach out to us for more details about those situations).

If the clients gave you 50% less price, and he told you that you are charging way more and it's so expensive! you can share with him those pictures for other service providers experience , and tell him : cheap is cheap, and it will never be good ! and good is not that cheap , and you can see some of the cheap service clients feedback ! you may like the price but how someone can buy chemicals for 350$ and professional machines for 10 000$ and the cost of service is more than the service itself ! 

see yourself of they are satisfied (share pictures after this)