http://www.netmagazines.com/categories.asp?cID=9

I just renewed my American Girl Magazine for one year. This is the best price I found.
Net Magazine's price is $15.95 for 1 year.
Plus, I got this coupon code in an e-mail RENEW05 for an additional 20% off.
So, your price for one year is $12.76. The AG subscription price is $22.95, I believe.
I have ordered magazines from this website and never had a problem. You can even pay with Paypal.