Refillable, but how?

I have always been a fan of Staedtler Lumocolor markers. I have full sets of 8 colors of both permanent and non-permanent markers, at home and at work. They are high-quality products that perform well and last for quite a while. Nothing, however, lasts forever. Upon discovering that one of my sets has dried up, I set about researching how to take advantage of the "refillable" option that is stamped on the side of the markers.

The refill option looks very neat and convenient. You stick the marker in a base, and it sucks up the new ink until it's full, then stops. Sounds cool. There's nothing wrong with my markers, other than being dry, so this seems like the way to go... except for a couple of caveats. Despite all 8 colors stating they are refillable, the company only lists 4 colors of refill tanks available. When I researched the price of the refill tanks, I was shocked to see that they are approximately $15 per color. A new set of markers, under corporate pricing, was only $12. Since I do not go through markers that quickly, nor does anyone else in my office use these, buying the refill tanks for only 4 of the colors doesn't make any financial sense.

What frustrates me is that Staedtler seems to be promoting an environmental angle on their website with their "efficient for ecology" tagline and program. They promote the refill option, but don't offer it for all colors of the same product. If it is cost-prohibitive for an occasional user to refill rather than re-purchase, how is that ecologically friendly?

If I had an office full of co-workers who all used these markers, the cost of the refill station could be spread among many people and would end up being cheaper overall. For a single user, it is cheaper to throw out the old and buy new. Why do they not have a single-refill option, perhaps not quite as slick, so that us Average Joes could benefit and do something more environmentally-friendly?