I don't get how people value miles sometimes.

For example, there are some bloggers who say they used x number of miles for a 32,000 first class ticket! "That's 16 cents per mile!" But no, because you can buy miles for 3/3.5 cents per mile, so you have to be really stupid to actually buy the ticket, considering your credit card miles and "paid" miles take award space from the same bucket, right?

And then there's milevalue and lucky who more sensibly value the miles at a fixed amount, like 0.8 cents for Hilton, which is slightly better, but that doesn't make sense either because your cpm redemption value is dependent on the actual redemption. So what they're saying is like "I value 100 USD at 80 USD, but since I got 100 USD worth of stuff, I made a good purchase."

That simply doesn't make sense to me...