This just in to add fuel to the fire : Linkage , an official bethesda stickied post from theelderscrolls.com forum. Heres a quote :
"We hope to have The Orrery available for purchase next week. This plugin will cost 150pts on Xbox, and $1.89 on the PC. The Horse Armor Pack has been very popular, and exceeded what we thought it would sell. Despite that, were still trying to find the right spot, so were putting a much larger plugin out for less than the last one and we'll see what happens. Your feedback as we move forward in this is invaluable. Tell us what you want to see, how much of it, and what it might be worth to you. No, dont say you want it free, because these plugins take a surprising amount of time to create, polish, and test (much more then Morrowind's)."