The best thing to do is this:
Have a contractor give you a FREE ESTIMATE for the home (size, levels, finishes, etc) you want built. Then contact a Monolithic Dome Builder and tell them basically the square footage you are looking for, the number of levels you want in your home, and same typical information as stick home.
Most dome builders will quote just the SHELL due to the fact that everyone has a friend, cousin or something that does "construction" and most clients want to hire them cause they are cheaper. Maybe the could offer some "consulting" for a small flat fee or price out a full "turn-key" dome..??
The experience I've had so far is that finishing the interior of a home is a little more than the cost of the shell. The cost could be anywhere from 110% - 200% depending on interior styles and finishes. (tile vs carpet, granite vs Formica, oak vs pressed wood)
Hope this helps.
If you need some numbers (without going overboard on my time);http://www.jdsdomes.com