Since most Realtors(R) are not also builders we tend to use website tools to provide rough estimates for our clients until they are able to contact someone from that trade. This website may provide the information you're looking for on contruction costs. http://www.building-cost.net/
Keep in mind, you will get a more accurate answer by providing correct answers to their questions. You may also want to add to the estimate for potential cost over runs.
"Green" is a very subjective term, so I cannot answer that question about less expensive. If you are referring to less expensive to build, I believe the answer would be "no". I believe you will find construction more expensive, and costs will be recouped over several years in the form of lower utilities and perhaps maintenance on the property. However, this would depend upon your, or your contractors considerations during planning and construction. I have someone from the Grand Rapids area that may be able to provide more information and references to builders.
When considering green, you need to ask questions about HERS rating (I believe 65 or better is considered green) or LEED rating for the home.
You may be able to find more information to help you on this at http://greenbuiltmichigan.org (website was not available this morning) or http://www.usgbc.org/ which has a green guide on the left hand side of the screen.