I agree that Southwest should treat member+companion bookings as a bundle. Once booked with a CP it should allow changes, etc.

In the meantime it's a boring/inconvenient workaround, but you can also search your email for the confirmation # and amount paid. At least Southwest still shows the price on the confirmations.

Also, look at the estimaed # of points earned on upcoming itineraries, this will get a good idea of the total paid. This is another way it's good to do one way trips, so that you can see the amount paid each way.