A few days ago I "discovered" a webpage where users can sell their games, and got Final Fantasy III (DS) pretty cheap (8 dlls/shipping included). With that I only need FFV, FFXI and FXIII to have all the numbered games of the series.
I know, it's not going to be THE Final Fantasy collection, but as long as I can say "I have all of the numbered FF games" I'll be happy.