The biggest problem is Astral Diamond costs. While several of the currencies used for Strongholds can be handled as something that guild members need only for the Stronghold, everyone needs Astral Diamonds on a routine basis, and it’s not fair for players in smaller guilds to more or less give up all of their diamonds. The new costs are thus based upon guild size, with the expectation that members will “tithe” a portion of their Astral Diamonds, so smaller guilds will see the biggest discounts. There are other cost reductions in place to ensure that Strongholds remain a lengthy project without becoming an insurmountable one.
Neverwinter originally priced Strongholds on the high end for two reasons: First, Strongholds were meant to be a long-term project, and second, it would have felt much worse if prices were raised after the fact. But some of the prices on Strongholds are just plain higher than they ought to be, and the most recent developer diary on the subject explains exactly why the prices are too high and what’s being done to fix it.
Source: Official Site