It is easier than you think - value-added. For each GO benefit you receive, you assign a price tag. Then you add everything altogether.

For example, I did 9x HKG-SFO in Y (M, L, V: 70 CP/trip) each year. In those 9 trips, I sat at an extra-legroom seat ($150) each time . I visited the lounge ($50) each time.

Without adding the priority services (baggage, check-in, etc.), the perceived value of GO would be $3,600.

Of course it is not ideal. But at the minimum, this calculation may be worth for someone to think about if MPC is really for them or not.