Agreed 100% Bruce, and I'll add something extra.
Movie nerds my age (and non movie nerds) grew up on VIDEO, it played a big part in our young life and teens.
Bigger than Cinemas and drive ins (well they were still around and important) but VIDEO STORES were great - and the art of the video posters, especially if its the same as the video cover, brings back all those memories.
Horror lovers tend to be extremely passionate about "their" genre, and as is usually the case, Collecting comes from Nostalgia, the wonderful day when you finally found a copy of SUSPIRIA on Beta, or ZOMBIE FLESH EATERS.
EG, I never saw a Texas Chainsaw massacre Daybill as a kid (even though it was banned here until the 80's), but I sre as heck remember the video poster and lifesize cardboard standee. And I'll tell you which id pay more for, it aint the Cinema release.
Its all about memories. And us kids have now grown, and some of us have money.