Looks like there are two sides here. One it seems is debating for the use of mods, and as I interpret their claim, things like led mods, changing boards to be more reliable, adding floor lighting or invisiglass. There wouldn't be any harm in doing this to a personally owned machine or for resale. These are not generally mods that are going to use any specific licensed characters, art, or likenesses.
The other side is debating something like this: Stan.Lee owns spiderman. Pinsider one draws a unique piece of art with a picture of spiderman. He manufactures these and sells them to other pinsiders for profit. Stan Lee sees zero dollars as a result. Problem. You're both right. Another group debates stern is at fault for stealing the idea that "ideas are possible for our machines and is in a much better financial and logistical position to make them. And hey, we are capitalists (for the most part. Don't really know everyone here) so why wouldn't the person best suited for a task make the money for doing it. But pretty soon the same people who claim the manufacturers are stealing will shell out for the factory le modded edition to the tune of 8-10 grand extra a pin because it's "pure"