I finished the Garter Yoke Cardi in a day over a month. Although that month was February, so technically I finished in 29 days which is less than a month for every month except February. Point is, this was by far the fastest knit for a sweater.
It was also the cheapest! I used Lion Brand's Fishermen's Wool. It wouldn't be considered a high end yarn, but it's warm and I have read that it tends to soften up with several washings. The best part is that it was $6.40 a skein with a coupon and I only needed 2 skeins. Can't beat that! I did spend an extra $5 for the buttons (with a coupon of course!), but I had store credit, so I don't really count that as part of the cost.
The sweater is a perfect fit, which is one of the benefits of making your own clothes. My one minor criticism is that it ripples a little where the buttons are, but I was assured that it doesn't stand out too much because of the color of the yarn. I can deal with a little rippling on the button band (although I would like to learn how to avoid this) if it means the sweater isn't baggy.
It has been really rainy and cold here, so it is the perfect weather for a nice cozy sweater.