United is offering the following on Buying miles: Here the link

http://www.ualmiles.com/PersonalMile...2.x=26&x2.y=18

Buy miles and save now


Save now and you'll save at least 20% when you buy Personal Miles or Give Miles. Even better, if you buy miles while they're tax-free, you'll save an additional 7.5% - that's a savings of over 25%. Remember, the tax may be re-enacted at any time, so hurry! Offer ends July 31, 2011 at 11:59 p.m. CST.


New! There is no longer a processing fee to purchase miles. However, miles now cost $35 per 1,000 miles
For a limited time, miles cost $28 per 1,000 - a 20% savings
Miles cost $35 per 1,000 miles
Purchase up to 60,000 miles per calendar year
Minimum purchase of 2,000 miles per account
Credit card will be billed immediately for purchase
Program fees and mileage rates subject to change
Allow 48 hours for miles to process and post to your MileagePlus account
Miles are available in increments of 1,000
Miles are non-refundable
Miles do not count toward elite qualification
All standard MileagePlus rules and conditions apply