For FOM configurations, you can choose between using the PPA price or retail rates on the Electricty Purchases page:

For the retail rates option, SAM reports a bunch of electricity bill outputs that don't apply in this context that can be confusing.

To avoid confusion, FOM configurations should only report electricity bill outputs that are relevant, including "with system" outptus and outputs for buy/all sell all metering option. "Without system", "savings", net billing, and net metering outputs do not apply.