Believe it or not, amazon.com sets different prices for the same items, depending on whether you are a member or not. In other words, if you want to buy a dvd at $30, and you are a member of amazon.com (you've registered at the site), that same dvd may be available for a higher or lower price than you were quoted. Try this: clear your cookies, or visit amazon.com without signing in or logging on to the site. See if the price is cheaper. I'm not saying that it will be cheaper, but you never know.
I always visit amazon both ways...as a logged in member, and as a guest...just to see if there are differences in the prices of the things I am interested in. Try placing your dvd in your Wish List at amazon.com. The price will invariable rise, as amazon.com knows you are interested in that sort of dvd. It is a scam to gouge registered customers.
You can probably get a cheaper price by visiting froogle.com and searching for the best price for what you want. Also, at amazon.com....visit the Merchants marketplace for your dvd...don't just accept amazon.com's price. The Merchants will usually offer the product cheaper than amazon.com.