LR refused to make them US DOT compliant with airbags and such or meet more stringent emissions requirements, so there were only a few years you could get them and at that in limited numbers. The bodies are aluminum which makes for another premium, but mostly it's the scarcity+popularity=exclusivity equation. I came very close to purchasing one (much against my "no British cars" rule) from Reeve's LR in Tampa back in '95, then they were gone in '96 and back for just '97 and that was the end of that. From there they've not moved very much from the original sticker of just over $30K.

Now there are alternatives however, as you can sometimes find "imported" both the Defender 90 and the 5-door Defender 110. These are the military versions of course, but that gets you a diesel option as well. Getting them in is the tricky part as you can currently only import a vehicle over 25 years old to avoid meeting DOT and EPA requirements, but there are exceptions and grey areas if you've got the patience and $$$. Here's one exporter specializing in LR and they've got some basic info on what and why you can't bring in: http://www.landrovercentre.com/usa/which.htm