I have different valuations depending on if I have to buy the miles such as a USDM or Avianca 100% deal or if I get them for free by signing up for credit cards or directing my normal spend to one card vs another, or other free things such as E-Rewards, E-Miles. I don't value the time I spend doing the surveys because I do them while watching tv (I'm a good multi-tasker) so I am not wasting time I would otherwise be using more profitably.

The 100% buy miles deals, I only use them in moderation to cross the threshold if I am close to a redemption level.

If I have to put a dollar value on my redemptions, I use whatever the lowest cost to get from A to B is, because I would never spend cash on a full fare J or F seat.

I also take into account how difficult it is to get the miles or points vs how easy it is to redeem them. I find more value in miles such as AA and UA which can be redeemed for one-ways than others like US and DL where you have to book a return ticket. I take into account if you can book it yourself online vs having to call the airline to book.

But no, I don't put a $x.xx per mile cost on my valuations because in my case it's either use the miles or I can't afford the ticket at all.