Using kiosk check-in on AA gives the option to buy double or triple miles for the trip, and the rate for these miles appears to be variable (at least I've gotten offers at different price per mile), with the cheapest being 1.5 cents per mile. I have no idea if this is by route, status, time of month ... but AA is doing everything possible to sell more miles. Same for other airlines in NA, for example USAir was offering me 300% bonus in miles bought which made it about 1 cent/mile).

Valuing FF miles is soooo dependent on the proposed use. The airlines expect 7% of FF miles to be redeemed, with 93% to expire unused. This assumption is becoming increasingly unrealistic, but the problems are for the user and not the airline. The last 10 times that I've tried to redeem Aadvantage points there was no reasonable availability, for example -- even paying double for anytime awards. Given the easy acquisition of miles by just about anyone, this is hardly a surprise. The FF world has changed and factoring in ability to redeem miles is now a big part of the mile valuation. The more flexibility in dates/routes that you have, the more miles are worth.