Nobody was willing to give $9000 for it. That number is the value of the in-game price in ISK, then converted to $. It's not even a good ship, only a rare and thus expensive one in game's terms.
No. I think what he meant was that let's say people are willing to trade X ISK or whaever it's called for 1 USD, and the spaceship is 9000X ISK therefore it might cost 9000 USD.
The conversion/trade I suppose doesn't always work that way.
The game devs sell game time for real cash. When you buy some, you get an in-game item called "PLEX", which you can either convert to 30 days of playing, or, sell for anyone in the game in the in-game market for in-game currency, at whatever price you both agree to. This creates a floating exchange rate from $ to ISK, by which count the Revenant was $9K. However, since the conversion is one way, it's questioned whether this means the ship can be said to be worth $9k.
$ -> ISK is a one-way conversion, which creates a lot of debate over the definition of "worth". I'm not enough of an economist to have any idea over which definition is right :P
There are unsanctioned (might get you banned) ways to convert ISK to $. The unofficial rate is of course much lower because of the risk, but even counting that way, the Revenant was worth $3k.