I remember back in the early 90's the Diamond Stealth 64 that used the S3 Vision 964 chip and had 4MB of VRAM was around $500.
The Vision 864, a cheaper version that had I think 2MB of RAM went for much less, around $250-$300.
So, $400 for a top-of-the-line video card is not anything new in the world of PCs. Actually, for what you get, it's quite cheap, based off certain reference points!
*EDIT*: edited stealth -> stealth 64