There are huts, emergency shelters and earth huts.
Huts are serviced, have heating, proper kitchen, water, loo etc. and are costly.
Emergency shelters are not serviced, have an outhouse, mostly a water source nearby (
not in the case of Kistufell eg.) and same goes for earth huts like the one at Laugarvellir (stupidly great spot with hot pot, some amazing moon-like landscapes and enjoyable double tracks and hard enough surface to go completely cross country w/o leaving tracks just right at the "doorstep"). I never slept in a shelter but came past some and I can't remember any charges. Definately no charges for the earth huts.
Here's another map for Basecamp and GPS (works just fine on Edge 810)
http://www.ourfootprints.de/gps/mapsource-island_e.html