I have 5, with 2 interior pages from the same run. One thing I like to do is compare different styles by different artists of the same subject matter to see how they handle it. So for me, an unpublished page is often a treat because an unexpected artist shows up drawing a Phantom Stranger image. On balance, they cost less, and are worth less, then a published page, but as noted above there are exceptions.
I have 3 different pages from two cancelled series where DC was trying to unify all the different magic types. One attempt was to unify all the different magic types into a single magic theory (the artist, Chris Schenk, had only done the pencils, so I commissioned him to ink it privately, very pleased). The other was an early attempt at something like a Justice League Dark that went nowhere (with insane looking characters, but pretty good art, by Duke Mighten). I also have a tryout page for a Constantine book by Jason Shawn Alexander, and a very good pencil cover by Scott Clark to Phantom Stranger No. 3 (4th Series).