I've seen open GT's go for at least $1200. Personally, I don't understand the point of buying sealed anything - unless it's so cheap, that the money is no object (not because I expect to use it, but because I get most of the enjoyment of what's in the box - even if I don't play it).
Of course, "cheap" is different things to different people.
Came on, guys. The first post is of 2005. At that time I'm sure there were some GTs selling Brand New. The last I saw in MINT condition (but not new) was about 4 years ago sold here, in this forums for 600€ I think.
I bought my GT in quite mint condition for around €600 incl. shipping in 2015. I posted details here. But you can’t find them at those prices anymore. At the time I already thought it was not cheap compared to stories of what they had been going for in the past, but I felt given the then-current prices it was a good deal and I had to jump on it because prices were only going up :). If I were to sell it now, I would try to get around €1000 for it probably. Though of course, I’m not gonna!