Yep. I saw one on the road a couple of months back here in Fort Worth, and thought "damn that's a beautiful car...I wonder what it would go for these days?" Was astonished to learn that the prices are just as high as the day they came out.
Porsche 993's are holding their value too and seem to be well on their way to collectible status.
Yeah, the Z8 has almost never dipped below current market prices as well. Would be a good buy for a collection. I went to school with all the Wal-Mart family kids and they bought new cars constantly, I remember one of them pulling up next to me in the Alpina version of the Z8 (this was back when it was a new car) and getting my mind blown. They had the usual supercars and stuff but that Alpina really made an impression on me, especially since it was in the middle of America.
All air-cooled 911's are worth good money, can't even pick up a mediocre air-cooled 911 for less than $20K anymore, 964 or 930. 993's are slightly inflated on the US market, by maybe 20%-30% I feel. There's 993TT's that sit on ebay at $80K every day of the year. I'm whittling down my car list still and the 993 keeps popping up because of it's insane value. I could pick up a 993TT for about the same or less as it'd cost in the US, a rare occurrence. It's pretty tempting because I know that if I ever wanted to unload it later, the market would be solid. Those 993 C4S are worth a ton too, almost turbo prices.