It's a different beast. The price is high during those 15 minutes because of supply and demand. If you implement a smart grid that regulate load, you upset the supply and demand balance and the power might become so cheap that new self regulating systems are not worth the initial cost.
Once the smart-device interface is properly defined and the software is written, the hardware cost should not be a problem.
You will end up with some kind of "smart device" router that connects to your internet/home network to talk to the power company, and uses a commodity wifi interface to talk to your smart devices. The cost of an ESP8266 is already sub-$7 at hobbyist volumes, you can expect the additional hardware cost to easily be driven to trivial levels with widespread adoption.
The problem is purely in getting a standard system out there and designing devices that incorporate the new control model.
It is completely unnecessary for appliances to talk to the power company. They only need to talk to the internet. The power company just posts the spot price on a web site.
The appliances won't talk to the power company, they'll talk to the appliance hub. The appliance hub will be the one with the logic to handle temporarily raising the thermostat or whatever, and will handle the internet connection.
Also, using a website or other resource run by the power company is still talking to the power company. Not sure ho else you could have parsed that, but you clearly had some crossed wires there.
