Sorry bout the quality, it's the only pic i have of them on my car.
17" Cup 1's (or design 91's as they are officially know) are available in a range widths (7-9.5) and are most commonly low-pressure die-cast. They were also available in forged magnesium but only in 7.5 and 8.5 widths (they go for approx Ԛ£2k).
A set of 7's and 8's (same as mine ) will set you back about Ԛ£600 upwards from most specialist breakers, but if you know where to look they can be had for much less. I payed Ԛ£380 for mine, and sold the tires for Ԛ£100. So Ԛ£70 per wheel, which was reasonable i thought. Most important to me was that i had something individual on my touring, which isn't easy when it comes to e30 wheels.