...they are SIMPLY TOO HIGH.

Ah come on, its not that hard to earn some money.  I... already [own] 10 chunks of vulcano

... the prices could really be too low.

... the prices of wilderness plots get exorbitantly high within a fairly short amount of time.
... keep large growth of people's plot sizes in check, and to prevent a large number of inactive wilderness buildings...
... taking over half a year just to get enough terrain to get a 100x100 building seems ridiculous...
Note: this quote was before the recent decrease in plot prices

With some players still worried about plot prices being too expensive and some content with the current prices, I would suggest a system called "auxiliary plot allocation" (APA).  This would be an application that gives players extra land at a discounted price, as long as they provide extensive evidence that a 'large build' requires this land; maybe the application would require screenshots of test builds in creative.  APAs would allow large builds across the server to be monitored by admins, instead of low prices causing land to disappear to the whims of an overly-ambitious millionaire.

Pros: Save money on legitimate large builds.
         Avoid doing a flat-lowering of prices.

Cons: Bureaucracy.

Thanks admins!