You are reading it right... although with the armor save capped at 1+ now, enchanted shield isn't all that necessary. Just take a mundane shield and a dragonhelm.. cheaper and you are immune to fire (basically).
if its cheaper in your armybook, then you use that cost instead i do believe. I unfortunately don't have ether on me to cross check but I think thats how its ruled in the FAQ.
Yeah, use the rules for the item in the BRB. The price for the item is ALWAYS the army book price. At least the war banner is only 25 points for us instead of 35.