CDTradepost.com
Nightmare on Elm Street Box Set: $24.99 + $5 shipping
Friday The 13th: From Crystal Lake... $35.99 + $5 shipping
They'll be from different locations, so you'll pay shipping from each, but they're still the best prices I've seen. Highly reputable, almost always great condition DVDs/Games.
You have to call the location that has it to order, so you can ask them at the time to check the condition, and to resurface/buff them if they're scratched up. (they do it professionally with a buffing machine, no nasty swirls afterwards).