I think the "liquid gold" Castrol alone goes for 12 bucks a quart or more at retail. The car takes 9 quarts.
I paid about $180 all in. I knew it was going to be expensive but that surprised me. (I've also replaced the PS2's already - thankfully I only had to shell out for the 18's - a little over $1,200 at TireRack.)
Not a cheap car to own - but I agree that I'd never let it go 15,000 miles between oil changes. I want the thing to last, so I'm paying for at least one change between each scheduled one.