Serum-Free media are expensive but do outperform serum containing media. To be honest with you I have used Gibco's Sf900. Sf900II and Sf900III and several other manufactures serum-free media and the new Sf900 III media is the best I have used. The problem you will face if you switch is adapting your cells to a new media. I went over adaptation in a previous question today that is archived on this site. I have done studies comparing media and when I say outperform I mean with both virus titer when amplifying your virus and also for recombinant protein expression. I think you stated it correctly that good and inexpensive don't go together when talking about a SFM culture media.