[margalabargala]

Only sometimes. Depends how you use them.

If you have some specific flight that you pay for regularly, e.g. to visit family, then replacing that flight's average cost with points gives a concrete number on point value.

If you are using points to fly first class on a trip you would not be taking at all but for the point redemption, then the value gets a lot more muddled.

[ghaff]

Absolutely. If you use points for something you'd pay cash for otherwise, they're typically worth something like 1 to 2 cents per point. But a lot of people (and I've done this myself with upgrades now and then) treat them as more of less "free" money. Presumably the upgrade or whatever has some incremental value but we wouldn't have paid for it out of pocket.