I started building up my original Xbox collection around last year, after someone sold me theirs + 8 games for 25 bucks. Pretty much all the games worth having for that platform are dirt cheap, but probably not for much longer. I wanted a physical copy of Silent Hill 2 for the PS2, but even a loose disc alone goes for like 100 bucks. Compare that to the Xbox version of Silent Hill 2 which you can grab now for 30 bucks CIB, maybe a little more for a sealed copy. Otogi 1 & 2 were super cheap but are now slowly going up in price because Souls fans want those early FromSoftware games.
What I'm saying is, if you're at a used game shop and happen to see copies of Panzer Dragoon Orta, Jet Set Radio Future, and Shenmue II... buy that shit and hold onto it!