How do airlines pay for their planes?
The overwhelming majority of major airlines do lease at least some of their aircraft. And most airlines who choose to buy do not end up paying that full price tag.

In the case of Easyjet, around half their fleet is leased (as of 2013). Leasing allows airlines with weak balance sheets or with poor future prospects to increase capacity without locking capital.

In fact, the largest aircraft owners are aircraft leasing companies. For example, GECAS (General Electric Capital Aviation Services), the largest aircraft lessor, currently owns around 1,700 aircraft, being operated by 230 airlines around the world.

There are other (not state-owned and generally low cost) airlines, such as Ryanair, who are fond of owing most of their aircraft. What Ryanair does is negotiate very good procurement deals with Boeing (by buying large packs of planes, all being B-737s), use them for around 5 years, and then sell them before their price has gone down too low. This takes a burden on their debt levels, but seems to work for them so far on the long run.

This aircraft resell value is an important aspect to consider when comparing leasing vs purchasing, as well as tax incentives derived from amortization.

Legacy carriers (many of them state owned), on the other hand, have a tendency to purchase most of their fleet, and keeping them around for the full lifespan of the machine (around 30 years).

The actual price a company pays for a given aircraft is not public (understandably) and most figures you would be able to find are related to "list prices". However, in 2005 Ryanair was forced to disclose facts about one of the massive (by the time) purchases of Boeing aircraft. Apparently, they paid less than half of the public list price.

More current data on the actual price airlines pay for Boeing planes can be found here, where Javier Irastorza analyses the discounts Boeing is applying to their aircraft based on a balance sheet assessment.