You seem to be suggesting that cost should be a deciding factor in whether to protect creative work. I disagree that there is a difference here between copyrights and patents.
1) In the tech industry, calculating the "cost" would be anything but straightforward. What would be allowed and what wouldn't? The players are not even comparable - what would stop a large corporation to include their HR, legal departments, and executive team as part of their "R&D costs"? Whereas, a small software startup with 1-3 members getting paid ramen noodles would be hard pressed to properly chalk up a tiny fraction of the costs the large corporation. The large corporation would have no problem showing that "project X cost $1million+ in R&D costs" while the startup would be in $thousands or $tens of thousands. If anything, one might argue that the OPPOSITE of cost would be better indicator - I see more innovation deserving protection from small startups creating things in a weekend than large corporations pushing some new technology developed over years using teams of people and resources.
2) There exist numerous examples where traditional artists create works in relatively short time. How many times have we read about an artist who wrote a song in an afternoon or even an hour? In those cases, the "R&D" costs of creating the song or painting would surely be considered small (if not tiny) when compared to tech R&D. It's contradictory to suggest that creative works protectable by copyrights at times with lower "costs" should be more protectable than tech protectable only by patents.