With nocturne, it's still not bad as I've seen the soundtrack go for $10 while I haven't seen a complete copy of nocturne go for less than $75 for a while now. DDS1 with no soundtrack for $60..... meh, kind of the average ebay going rate.
I know the japanese "director's cut" of nocturne was the only version translated and released for NTSC-US and PAL.
DDS1 came in a collector's box with room for DDS2 and a soundtrack and I guess Atlus released an "Ultimate" bundle with both games in the box and some other goodies for NTSC-US. I don't know of any special releases for PAL though...