I feel it my duty to help out a fellow gourmet of tripe
Save your money. Don't go to Amazon, go here http://www.oldies.com
They have a fine selection of old B movies for as little as $5.95. They also do 30s serials (Flash Gordon, Buck Roger etc.) and boxed sets.
If you are looking for more up-to date stuff, Play.com do a triple disc set at £14.99 of Willow, Legend and Ladyhawke. They have lots of others at good stuff at competitive prices.
A particular favourite of mine is The Sword and the Sorceror which you can pick up pretty cheap now.