It's true the Copic SP Multiliner refills are expensive, but I just love the metal barrel. I've started refilling them myself by dripping a small amount of Platinum carbon ink into the cartridge once it starts to dry out (they're filled with a foam that the ink soaks into). I've found it works well, and doesn't seem to need much ink added in either, I last refilled my Copic at the start of the year and it's still going. I did notice the nib became wetter and the line heavier, but that may have been in comparison to a low ink cartridge, or I need to put a fresh nib in it, as they do wear down.

A great pen, but yes, the refill system is crazy really, and so wasteful.