the Rota Slipstream in a 15X6.5 weighs in at 11.9lbs and will cost a fraction of what you'd pay for any Motegi wheel..
I have the 16x7 0n my truck and those come in at 13.9lbs
and cost me less than $500 bucks.. (bought about a year ago)
lots of colors available and a classic 5 spoke wheel..
http://www.18racing.com/images/slipstream_all.jpg
18 Racing