I'm paying for watt?

Lately, I've been getting interested in those very expensive LED lights that you are starting to see in the aisle that has the light bulbs. The LED lights themselves can be up to 10 times the cost of your normal run of the mill tungston lightbulb. I started wondering if these things make any sense, so I put pen to paper (or cursor to spreadsheet) to find out if these things make sense to buy.
It turns out that they do make a lot of sense, with one caveat. That caveat is that they MUST last for 2 to 3 years.
Here is how I made my calculations: In my kitchen I have 5 halogen lights that are 75 watts each. I use these lights for about 4 hours each day, so to get the yearly kilowatt/hrs for these lights, I multiply (5x75x4x365) then divide by 1000 to get the total kilowatt hours of 547.5 per year. I then multiply this kilowatt hour number by the kilowatt cost of electricity in my area (about 12 cents). This gives me a figure of $65.7 which is the amount that I spend on electricity per year on these lights. The bulbs themselves cost around $10.00 each, and they have to be replace every about 2 years. So the total cost for 2 years for these bulbs would be roughly: $180.00. Which means about $90.00 per year.
For a set of LED lights the run down would be some thing like this. For the electricity cost, I calculate: 5x20x4x365 = 146,000/1000 = 146 * .12 = $17.52 per year for the electricity. The bulbs cost about $45.00 each, but they last much longer. If you only had to replace them once every 5 years, your are looking at a total cost of about $312.60 for the 5 years or 62.52 per year. That is the price of 5 LED bulbs plus the cost of electricity to run them for 5 years.
The standard bulbs would have cost around $450.00 during that same time. However, if the LED bulbs only last 2 years, then they would cost about $130.00 per year. If they last 3 years, they would have a yearly cost of $92.52, but If they last the advertised 10 years, they would only cost $40.02 per year. To make any financial sense they must last about 3 years. Guess what I will be buying from now on?