For value for money vs quality of product, some of the classical sets kick ass.
Complete Tennstedt Mahler £20, complete Abbado Mahler £30 (was nearly a ton) - The benchmark recordings.
Karajan complete Beethoven Symphonies £12, Klemperer complete Beethoven orchestral works £15
'Composers In Person' 22 cds of composers playing and conducting their own material £23, '20th Century Masterpieces' 16 cd Warners - £23,
Concerto Koln 'Play Dall'Abaco, Locatelli, Vanhal, Kozeluch And Eberl' - £16 - Really good! Would be worth it for the Vanhal alone.
Got around to delving into some of the boxes I'd picked up and just skimmed at the time, it's been good