I don't think there's a simple dollar amount that i put on my miles. I use them for two things: trips to Montreal a few times a year to see relatives, which are always at least $500, so to me a good deal at 25k miles. for two of us, $1000 spent today vs 50k miles that i already have in the bank is a no brainer. The other thing i use them for is vacations to exotic places i would never buy a ticket to. I would never buy a ticket to australia for vacation, i would go somewhere closer and cheaper... however i would spend a few hundred thousand miles for a couple of biz class tickets over there and enjoy the vacation of a lifetime. worth noting, i earn 95% of my miles on company paid business (free for me) and maximizing partner promotions (credit cards, 5k bonus miles for renting from a certain car company, etc). i've earned almost 50k miles in the last couple of months by simply renting and staying at the proper partner, when i have my choice of rental car and hotel anyway. so my out of pocket cost is essentially zero