I bought all the single and double issue reprints of EC from Gladstone/Ross Cochran/Gemstone in the '90s. Consequently, I've never felt the need to buy the collected editions.
A cheap source (i.e. free) for reading '50s horror are the public domain sites--Comc Book Plus and the Digital Comic Museum. You can't read anything that's not in the public domain (like EC), but there's a lot of other horror comics available on those sites.