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Huddler Bobkart developed a formula for computing the total (tangible) cost of ownership of light bulbs that takes into account the initial cost of the bulb, its energy consumption, its light output, its lifetime length, and the cost of electricity. The full analysis and explanation is below, but we'll start with the comparison of an incandescent, CFL, and LED lamp each with identical 800 Lumen output capabilities, but with vastly different initial cost, energy consumption, and lifetime length:

http://greenhome.huddler.com/wiki/lifetime-costs-of-light-bulbs

Incandescent bulbs are chaper to buy but so much more expensive in the long run. It is a lot like a lot of things that are purchased - quality may costs more startup but are much cheaper in the long run and better for the planet.