Web based simulation game

have a green research and development website currently under constructed. A large part of the company ethos, is to encourage green living. To promote green living in an interactive way, I would like to have developed a free to use social online game. The game would promote simple environmental science, as the proposed target area would include children.

The idea for the game is to have players build the most efficient village, using many different types of material. An example using a house:
1. In the building section screen, the player would select construction materials to build a house. The construction materials would simply snap together to make the house.
2. The player would then need to fill the house with domestic/electrical products, such as light bulbs, toasters, computers etc. The choice of products would be given in another screen, with the products energy breakdown and cost.
3. The nest stage is to test the efficiency of the house, and get an efficiency/cost score/green score.
4. In the town plan screen, the player would place the building in a slot.
5. The player can then repeat the process with other buildings.
6. The buildings would need to be joined up. Such as wind turbine to sub-station, then to house.

I would see this game as a cross between Sim City and Farm Ville.
Please give an estimation of the project cost. I understand that only an estimated figure of hours can be given, as I didn’t provide specific details. The estimated project start date is around about 6-8 weeks, and will start with pre-development.