I have no problem with mod makers turning a profit. Many mods require a significant amount of work and/or talent to make, there’s the upfront cost of design and manufacture when you don’t know for sure people will buy it, and then the pain in the ass of dealing with shipping and customer support. I’m not so entitled that I get mad at the thought of paying someone for their time when they make toys for me to play with.
If a mod is too expensive for your taste just don’t buy it - it’s not like you need it to play the game.