Why Does My Dermatologist Want Me to Buy Her Products?

I recently went to a dermatologist because I developed a rash on my face. I think I know what the product was that gave me a rash. I believe it was exfoliating scrub and it was too harsh. Still, I wanted to know for sure so I went to the dermatologist. She told me my toner gave me the rash, yet I have been using it for years with no issues. It is very gentle. Her solution was for me to use all of her products, especially the expensive serum that she “made herself.” Usually, dermatologists try to sell me expensive products made by other companies. But this clever dermatologist mixed all of her products herself and miraculously they were better than any product on the marketplace according to her. I don’t know why a visit to a dermatologist has to be so expensive.