[Graeme Dice]

These costs bear almost no relation to how difficult an item is to actually get in the game. Black steel full plate is available on Ulm units for only a resource cost. Elemental armour is only marginally more expensive than BSFP, with fire 1 added to the requirements.

A robe of invulnerability on the other hand, takes an earth 5 mage and 80 earth gems. You shouldn't be able to even buy such an item unless your nation also includes earth 5 mages as a standard unit, and has an earth gem income of a few hundred per turn. Otherwise where are all those magic resources coming from? A robe of the magi for only 480 gold is also pretty extreme, since it's normally an extremely expensive and rare item.

Giving a unit 30 protection for no research and only gold costs seems just a little strange to me.