Barozi on 07 August 2013
Fact is the majority of gamers never finish their games, thus your method would give the publisher less money UNLESS you double the prices, which doesn't make much sense either.
AC2 was finished by only 40% one year after launch and that is considered to be a big amount.
GTA IV was only finished by roughly 30%.
http://www.joystiq.com/2010/10/19/40-percent-of-players-finished-assassins-creed-2-campaign/
