The cost of the 230vac cabling down to your breaker box is going to depend on labor
and less on parts. If you go with a 3 string setup like these guys,
Gordy (7) on Flickr - Photo Sharing!
You will need 3 230vac cut-off switches going to 3 breaker pairs in your box.
I would do my own wiring, so it would be a lot cheaper for me.
Check out all those Gordy (n) photos.. They give you a good idea of what goes into a PV install.
There is also a video on youtube..