Cheapest is Stonehenge.
Most expensive is Three Gorges Dam... 90% sure. No resource to speed up production.
But I'm not 100% sure what you mean by consider production multipliers. It wouldn't make sense to halve the hammers based upon a resource as the possible multipliers would be: 100% from ironworks, 50% from power, 50% from buildings, maybe 50% from bureaucracy, and maybe 10% from state property, plus the base which equals 100%. Assuming all of them, maybe a resource wonder could be considered 3.6/4.6 times the total cost.. I think even assuming that three gorges would be more expensive than space elevator...