Sandman is a funny title, the full sets have always sold well, but you could probably piece them together individually pretty cheap.
Once you get past 1, 4, 8 there's not a lot out there that can't be had pretty easily for a buck or two.....I just don't think people care that much about owning a full set, the readers will go after the primo sets like 'Absolute Sandman', which at full retail is quite actually costs more (for now anyway). The speculators might jump on the full sets...
Yesterday, at the monthly comic show, there's a regular I chat with that's a pure keys speculator....errr collector I know, as he was walking out the door he bought a copy of #1. He had that nervous, guilty look on his face like he just been caught rubbing one out.....I imagine guys like him will all jump on #1, 4 and 8....don't know if they would buy the single non-key books.