It's still the same price as single phase down here, we just try to come off an existing transformer bank. Last go around single phase was only $100 less than three phase.
Most of the time if it's possible we try to come off an existing three phase service that's owned by the county or city. That way all you pay is the upfront cost for trenching in power and running conduit inside the building. No monthly meter charge that way.
You only encounter sky high prices when the power company has to run new primaries to your site. It's about $20.00/foot.