Which could be the best solution for Wifi Card for a project
Perhaps you also have considered the WiFly Shield https://www.sparkfun.com/products/9954 for USD 70.

Yes, that is expensive compared to, say, an RF Link Transmitter https://www.sparkfun.com/products/10534 for USD 4.

What you get with the first module is all the WiFi on-air protocols, and TCP/IP.  Awesome complexity and high power draw.

With the second module you don't get WiFi protocols, you have to use your own, and you have to buy a receiver module as well.  But the cost is great.  With a much lower power draw.

You might like to consider it as an alternative; wireless, but not WiFi.

(Disclaimer: a research institution owned by my government owns some of the patents in the WiFi portfolio, so I'm a beneficiary at a distance of the additional cost of the first module.)