When the App Store first came into being in 2008 the majority of new apps released were paid apps. Times have changed and more and more app developers are electing to go with free or freemium models rather than charging users to download their app.
Appsfire just posted their 2012: A Year In The App Store review that analyized the 1 million apps that have been sold in the App Store and they found that only 34% apps released in 2012 were paid apps – down from 74% in 2008.