The use of airpasses was historically a good way to get cheap flights, but for the most part that is no longer the case. It is rare for the fare on an airpass to be significantly cheaper than just buying a selection of one way tickets and in fact it is not unusual for the fare on an airpass to be more expensive.
One of the better examples of an airpass world wide is the 'flyabout' pass from Virgin Blue in Australia and New Zealand. This pass will not normally save you money on the fare itself but does get you some nice added extras.
On a Virgin Blue air pass you will receive 23kg of free check-in luggage, while on the cheapest Virgin Blue one-way fares you pay around $10 to check in a bag. You will also receive unlimited free date changes to your pass when making changes online. You can only buy the pass prior to arriving in Australia, but can also make free changes to the route you are taking prior to commencing travel.
