All of those CD's exist. I have all of them and none of them were made on demand. Yes, they're rare and were made in limited quantities though.
Well, it matters where you bought the cds..... You're fine if you bought them from a reputable CD store, but a lot of stuff online is fake.
Shit, a lot of artists I know drop an album, get 1000 pressed and once they sell them all they just turn around and bootleg their own album on demand. I mean your typical mom & pop stores will only buy 5-10 cds at a time and an artist may sell 20 cds at a show, so having another 1000 printed makes no sense when you can just print them yourself on demand..
I'm not saying your cds are bootlegs but what I am saying is there are a ton of bootleg cds out there...