Check out Benjamin Nevarez if you're still pursuing this. I had several exchanges with him a while back about how calculations were derived by the optimizer. This knowledge helped me figure out expected execution times. My last exchange if you're interested: http://sqlblog.com/blogs/ben_nevarez/archive/2009/09/11/how-the-query-optimizer-uses-statistics-part-ii.aspx

He ended up writing a book: http://www.amazon.com/Inside-SQL-Server-Query-Optimizer/dp/1906434603/ref=sr_1_11?ie=UTF8&qid=1301970045&sr=8-11

Good luck !

-Blake a.k.a CQLBoy