It's expensive because it's cool.
People like Steve, people want to look cool like steve. They buy his guitar.
If it was too cheap then people would doubt/know that it isn't really what he plays. If it was too expensive then people wouldn't ever buy it.
They picked the price that satisfies these requirements and also that of making money and paying royalties and all.
Hey come on, it is a buisness they are trying to make money. Everyone tries to make money. Soem take it too far-like Gibson or PRS maybe-I don't really think Ibanez is a company like that. You can get steve's guitar for under $2000 and you can buy J-Customs for less than 2 grand. There aren't too many companies that make awesome top of the line guitars in that price range. Try to buy a top of the line PRS and see the price difference. And the best PRS is no better than the best Ibby IMO.
Also, if you look at the artist that play Ibanezes that are predominantly like the ones we play RGs, JEMs, JS
and so on you can see that they are not only commited to ibanez for long periods of time they are also some of the best and most successful guitarist of all time.
Sure other companies have there super stars. But if you could throw down that Steve Vai and Joe Satriani and Paul Gilbert have played signature and regular model guitars that are all under $2000 for over 20 years, you would have a great company image wouldn't you. So if we really think about it, it's not "so expensive." No other company can claim that. Gibson and PRS sigs cost over $2000 for a cheap version (not counting Epiphone and Se models). Fender is the only company that can probably boast more than Ibby about affordable high end sig guitars.