A collection of 254 DARK SHADOWS VHS tapes is for sale on Ebay for 389.88, though you might have to add a wing to your home to store them. For comparison, DARK SHADOWS: THE COMPLETE ORIGINAL SERIES DVD set is selling for $349.96 on Amazon. I'm not sure that comparison is entirely fair, but you won't need to hire a private librarian to curate the DVD collection.
At about 7.5 ounces per tape, this VHS collection should weight about 120 lbs. Feel free to check my math, though.