The Price of Quality

I've been trying to buy some DVDs of classic movies, because recently we've been turning to classics when tired and stressed.  A few weeks ago it was Casablanca, and last night I watched the greatest music movie of all time - including even This Is Spinal Tap - A Hard Day's Night.  But what I really wanted to make sure we have are Top Hat, The Third Man, and A Night at the Opera.  Yet it's impossible to get The Third Man for under $30; Top Hat is not quite as expensive, but similarly uncheap.  Why are they so much?  You'd have thought less in terms of copyright issues, but somehow it's not the case.  

Regardless of the reason, it's annoying.  They're totally worth it, but I resent the movie peeps / retailers making these classics more unavailable to the masses.  Including me.