Tomaszkiewicz, developer of Witcher 2 believes that DLC should not have a price attached to it. He said that most DLCs are not worth paying for and should be free.
Talking to VG247 he further added that the people at CD Projekt consider DLCs to be just a normal post sale service and that it should be free.
We’ve always believed in free DLCs. The thing is that we consider DLCs as a normal post sale service, which shouldn’t be priced.
Back when retail games were dominant, we had expansion packs. These were really large chunks of content, which were worth their price. If today’s DLCs offered the same amount of content, they would be worth paying for, but in most cases players think they are overcharged for what they receive.
That’s why we offer expansions to our game for free. This is also a way of saying ‘thank you’ to the people who decided to buy our game instead of copying it from an unauthorized source.
So in simpler and shorter terms CD Projekt believe in providing free DLCs to show appreciation to fans for not pirating their games and instead supporting their studio.