As others have pointed out, subjective and objective values are different. I tend to use miles for international upgrades. Figure $550 or 30,000 miles for Y -> C TPAC, which works out to 1.8 cents/mile. But I think I suffer from what cognitive psychologists call the endowment effect, and would never actually spend $550 of my own money on the upgrade (and fuhgeddabout my employer reimbursing it). The miles, on the other hand, feel "free" somehow, like I'm not giving anything up, even though in theory their fungible with cash for certain transactions. The weird little psychological dynamic is that I might actually pay > 1.8 cents/mile, knowing that I'm converting cash which I wouldn't spend into miles that I will spend. It's kind of a moot point, since I have enough RDM's that I don't really need any more, but that's how I would justify doing something like using the Chase Visa to pay my taxes.