jmucchiello said:
Where are you going to house/feed/stall those 2500 archers and horses?
Think Mongols. Tents. Pasture. Wagon trains. Think Romans - we'll travel with some seige engineers, chop down some trees, dig some trenches around the camp. Set it all on fire when we leave. The simple question is whether a castle is worth the half million or million gps that could be spent on other things. Give me 2500 archers and horses and I'll GO GET the food!

(Food is not an issue mitigated by castle construction anyway.) Probably from the guy that lives by himself in his million gp castle because he can't afford servants.
jmucchiello said:
On the chart I quoted in the DMG a tower is 50,000 gp. That is functionally equivalent to the Instant Fortress. A Castle, based on that chart, would be much bigger than a tower.
10 instant fortresses vs. a castle is the comparison, etc. I don't particularly want to make too much of the example, the point is to question the value of a castle compared to the other things that a million gps get you.
jmucchiello said:
All I was saying was the cost of magic items is out of whack because all prices are squared. They should be linear.
They should be? On what basis? Magic items prices are completely linked to the gp/xp cost of creation. IIRC the price is determined by the gp and xp needed to create - what could be more solid than that? If it cost me 20xp to make a +1 sword, and 80xp to make a +2 sword, then the price is simply proportional unless you think there are other factors.
Now if you're saying that a +2 sword should simply be twice as expensive and not four times as expensive (and you reverse engineer the construction costs from that), I suppose that's your call as a DM.
A +2 sword is not twice as powerful as a +1 sword. A +2 sword adds a mere +1 out of 20 to hit and +1 out of 1d8 to damage. But then again, look at violin prices if you get a chance. A top quality sword would command prices far out of proportion with it's usefulness. Wealthy swordsmen would pay an arm and a leg for a simple +1 advantage by analogy to the violin example. IME my players certainly would.
jmucchiello said:
But, again, this isn't the thread for fixing D&D economics. (No thread can do it.

)
IMO it doesn't have to be all or nothing. The benefits of the thread are that you can raise issues. I'll work with any information that's posted.