I am currently working on a prefabricated dome kit which should be available later this year details of prices are to follow shortly.
If you are looking for a rough guide to give some idea how much a dome would cost to build I,ve made up an excel spread sheet to download right click the link to "save target as" I think it will also open in explorer. This is for a single skin structure you can enter the cost of materails to find out what the total cost should be, remember this doesn't include constuction costs