A quick glance at aa.com finds the following information on sharing miles, and yes, it will cost you $100.00:

https://transfer.points.com/AAdvanta...ethod=transfer

That's still less expensive than purchasing the miles, which would cost you $250 plus a $30 processing fee.

If you don't have an AAdvantage MasterCard, you can get up to 40,000 miles for signing up.

http://www.aa.com/apps/AAdvantage/Vi...artnersContent