I have this one, and I love it! http://www.imprezars.com/product2.htm#shift
Nice, short shifts, and the connection between the shifter and the linkage is a bearing instead of a rubber bushing, and that really helps the feel of the shifts. Just over $100 shipped, and Larry is a great guy, so I pimp him every chance I get!
I second the one from imprezars.com , the lenght is about the same as stock, shifts are much better. I actually cut about 2 inches off the top of mine and put on a sparco knob. I like the idea of a bearing too. Installation is easy.
Kartboy is the way to go...Tom and Mark are great guys, quality is top notch, and they epitomize "old school" when it comes to supporting the RS. Plus, they generally send you candy along with your order!
I've got the imprezaRS.com one as well, though i didn't like the bearings myself. I just coudn't get them to stop rattling at ~4k rpm, no matter how much grease and adjusting i tried! A few minutes pressing them out, a few more minutes with a coke can and some snippers, and i had the stock bushings in the short shifter. I lost a bit of crispness, but the throw is short and smooth, and it's quiet again. =]
I'm guessing that $240 one you saw was the complete lever/lower bushing/control arm setup. The $100 ones are just a lever and bushings, but they accomplish the same thing. In fact, mine feels waaay better than the STi unit to me.