Just so it's clear -- what the OP is talking about is not the old way of "using miles to upgrade a coach seat to First" -- that requires a minimum fare class (K) and upgrade inventory.

I used this on an LAX-ATL r/t. The cheapest coach fare on the days I wanted was about $500. In the past this would have been a K fare and I would use an SWU but with the re-alignment it was an L fare (IIRC) so no SWU. But a FC fare (G maybe) was $900 so I bought that, paid $500 on Amex, and $400 with PWM (i.e. 40K pesos). For that I got 150% MQM & RDM and no worries about a gate upgrade. I earned 10,700 SkyPesos as well so the actual cost was less that 30K.

Now some will say that is a terrible value for the miles -- but miles have no value if they are never used. I rarely use miles on myself and I figure I got value for it.