In the days of ST4, standalone autoguiding has a special market since it's bulky to bring and expensive to buy a laptop computer when you go imaging. However, the market landscape has changed so much so that the whole situation requires re-considerations. The low cost of consumer webcam is definitely important since they are not just cheap but they can also be used for planet imaging, they can also be used for guiding as well. Another important factor is the growing popularity of netbook, these small laptop computers are powerful enough to do autoguiding, they are small to bring and they are cheap to buy. And just like a webcam, it has multiple purpose, you can browse the internet, you can use your electronic star atlas, you can even control your DSLR but not just guiding.
In terms of cost, both are so similar these days. However, for the functionalities, you will simply find it hard to beat to webcam + netbook combinations! Of course, the simplicity of standalone autoguider could still be attractive, but it's not overwhelmly simple like in the ST4 era.