Home electricity costs around $0.15/kWh, while power plants sell electricity to the grid for around $0.03/kWh. The difference pays for installing and maintaining the grid and local distribution wires to your home. Depending where you are (I live in a forest, where a tree falls on the power lines a few times a year and they have to send out guys in a bucket truck to fix it) it's expensive.
Because of net metering, home solar panels effectively get paid the home rate. It's kind of unfair. If you have enough solar panels to zero out your home bill, you're getting something valuable (reliable nighttime power) that cost money (to install and maintain the wires) for nothing. But that's the system we have.
Sometime before we hit 100% solar power, the system will have to change.