I bought my CR system a little more than a year ago. I got two sets of replacement cartridges, and am about to put my last set in, so it was time to look at refills. I went to the place Mark mentioned, and the shipping was quite a lot--$45. So just out of curiosity I went to the CR site, to compare the total cost.
Well, everything is different at CR...they have changed the P/N's of the systems, the housing colors, they now have a battery powered purity meter, which seems to connect to both the inlet and the outlet, instead of the plug-in outlet meter, the carts have changed, it sounds like you don't have to pipe anything up when you get it, and all the pricing is WAY up. The big system is almost 150% of what it was last year, and the resin pricing is up almost as much.
The good news is that CR now has some resin options. You can still buy the replacement cartridges, but you can also buy pre-measured bagged resin to refill the cartridges, the cost of this is about 2/3 of what the replacement is, but you can also buy bulk resin from CR. It's a bit more than the place that Mark linked, but free shipping, and I think we Autopians get some sort of discount, so the price will be maybe a little more than half of the replacement cartridges, and about $30 less than buying from kfswater.
I'm not sure if resin prices have increased since last year, and this is responsible for both the higher resin and system cost at CR, whether they were using some cheapo resin that was the root of some of the quality problems noted in another thread, or simply that CR is capitalizing on the popularity of their system to make larger profits. I suppose a bit of it could be that they now have free shipping on everything, and have really just added the shipping cost into the price.