I noticed the same thigns as you did regarding wattage and prices when I was loking into this, but I decided to look a little deeper into the long term differences on simple purchase costs.

Now, looking at these two options:

GE Soft White Double Life 100-Watt General Purpose A19 (6 Pack) - 49345 at The Home Depot
Philips 70 Watt T60 White Halogena Energy Saver Light Bulb, Dimmable 2Pack - 209692 at The Home Depot
The incandecents put out 1555 lumens at 100 watts and have an average lifetime of 1500 hours.

The halogens put out 1600 lumens at 70 watts and have an average liftime of 3000 hours.

So basically, looking at the average lifetime ratings, 4 incadecent bulbs are worth as much as 2 halogen bulbs as far as time goes. So in order to make it more cost effective from a pure long-term purchasing perspective, the cost for a halogen bulb must be lower than double the cost of an incandecent bulb.

In the obove instance, the incadecents are about 59 cents a bulb and the halogens are about $4.49 a bulb. As far as purchasing goes over time, the incadecents end up being much cheaper. The halogens only offer a minimal energy efficiency boost though, especially when one considers that other options offer much greater energy savings potential.

However, CFL bulbs look to be the best bang for the buck in all respects.

EcoSmart 23-Watt (100W) Soft White CFL Light Bulbs (4-Pack) - ES5M8234 at The Home Depot
1600 lumens at 23 watts with an average lifetime of about 10,000 hours.

This means that the CFL can be 6.67 times as expensive as the incandecent to have the same long term purchase value.

But these CFL's are about a buck each. Meaning that over the span of 10,000 hours, you'll have to by 6 or 7 incandecents compared to one CFL which means you'll spend about three times as much using the incandecent

*without* factoring in the energy savings from the 75% decrease in energy use.

Now, while this doesn't take into account the energy savings, it also deosn't take into account the delay that CFL's have, the fact that they can't be dimmed, or other issues that they have. I just looked at things from a pure long-term purchasing costs perspective.