Opel Isignia Co-painting necessary?

Hello, I have a demand for someone who knows how to paint. My Opel Insignia BJ 2021 has a dent at the front passenger door below (is located in a circle on photo), but is only in the door not at the Holm or something. Was now in a paint shop (small place and not so much possibilities because of comparison ) and I have been told a little more expensive, because he has to paint the back door with, as I said the dent only at the bottom of the passenger door. # Now my question, does someone know if this is so right or that is just money making, because I don’t quite understand the meaning.