Interesting take on a bonus for buying miles. The base bonus over the next 3 days is 30%. Depending on how many people buy the bonus rate increases up to 60% if they get 1500 or more buyers. http://www.ualmiles.com/PROMO_buymilessept2013.jsp? Miles are pricing out a 3.7 cents each with a minimum of 5,000 purchased in this promo. That translates to ~2.35 CPM if the 60% bonus rate kicks in. That's still something of a premium, but it is an interesting marketing approach.