I think two useful ways to look at valuation are as follows:

If you receive miles/points in a transaction where you cannot find a tax rule that allows you to exclude the "income" on your tax return, what "value" of the miles/points would you list as "income"?

If you were making a loan to someone and he listed the miles/points as collateral, what "value" would you assign to this collateral?

Do I hear a lot of $0s?

To me, these miles/points are simply a coupon system that allows me to buy travel at a discount. I almost always have to pay something when I obtain miles/points and I almost always pay something when I use them. The value of what I purchase is the post-coupon price. The coupon itself had no value.

Most of the time I never would have purchased the travel at all if I did not have the coupon. Every once in a while I might use my coupon to buy at a discount the travel that I otherwise would have paid the non-discounted price for, but that is rare.

If I get a coupon to get an $8.95 burger for $4.95, I do not think that my coupon had a value of $4.00. That does not mean that I do not enjoy the burger I buy with the coupon. But the burger was worth the $4.95 I paid for it, not $8.95. The $4.00 coupon did not have any value to me. In fact, if I did not have the coupon I probably would have gotten a 99 cent McDouble off of the value menu, so my $4.00 coupon likely made me spend more than I otherwise would have.