You justify your price by saying "this is the price" and letting your audience be smart enough to look at the work and match the very high quality to a price point higher than what they may be used to.

If a possible client undervalues your photography, don’t waste your time trying to justify your fees. Assuming that they approach you because of your vision and your style, why would you allow them to undervalue your work and your fees? Of course you can negotiate and find a profitable agreement for both sides, but never if the starting point is undermining your art and your value. You are a photographer, you are not running a screw factory.

Facing clients who undervalue photography services can be frustrating. While it’s important to highlight your expertise by showcasing your training, experience, and unique style, detailing the time and effort that goes into each shoot, and presenting a strong portfolio to illustrate your quality, doing so defensively can feel desperate. If a client is genuinely curious and asks respectfully for details, it’s a pleasure to explain your process, approach, and share your work. However, playing the role of a salesman to justify your rates feels off. Mutual respect for professionalism should be the foundation of the relationship, and if it’s not there, they may simply not be the right client for you.

If they challenge the rates, I just say "I'm not the photographer for you." and move on. It's a fine line between justifying and educating. Usually they come to me because the reputation and published images/portfolio that drew them in. If they're inquiring about the rates, it's usually because lack of awareness. Then I find that a simple few sentences to briefly explain the work effort with pre/post process and skill is sufficient in just a couple minutes. They relate to you, not the details of trying to comprehend the craft. So a short answer that makes them say an excited "Wow!" usually works. If it requires additional effort to justify or defend, then it's not going to work out.