I suspect the profit margin on both inkjet paper and the inks themselves is rather obscene. It's basically just specially sized paper - no silver, no gelatin. I once saw the distribution cost of inks for high volume machines. They were marked up about a thousand percent by the time these the hit retail pricing. What they almost give away are the printing machines themselves. Once you've got that, you're hooked into refilling it over and over again. RA4 color printing is more economical.
Of course, even raw book paper has gone up quite a bit in the past several years.