First of all gear needs to have the same costs for military units as it does for champions or at least related costs. If an item costs a crystal and 10 materials and 5 gold to make have it costs 55 gold to purchase based on the value of the other resources so they are on the same level or no more than double what it would take to make it for a unit to represent the merchant's profit.
Secondly I think every piece of gear be it a weapon or an amulet should have a grade of quality. Minor magic items should be available earlier in the game as this is after all a fantasy game so you should have the +1 longsword hehe along with that 2200 gildar sword.
It would make sense if as your economy grows if little ancient trinkets and mighty artifacts come available to your city merchant in limited number. A band of might could become available on turn 2 but only 1 and since it is rare it might be ten times more expensive than it will be after you've researched how to make it yourself. Even after you advance in tech the really powerful gear should always have a limit and a refresh rate. You shouldn't be able to buy 10 complete sets of Legendary armor and swords at a cost of 10,000 gildar in one turn. It takes time for masters to craft mighty artifacts and the materials have costs and no armorer or weaponsmith is going to make a ton of items worth more than entire cities without a buyer for those items.
Allow the possibility of your champions buying and selling items to another nation's merchants. With the possibility of limited items this should be fairly useful and possibly a revenue stream if you've got a tech advantage and can charge a premium for advanced tech or magic items that they have a high demand for. You could also get a "rumor" that a certain wealthy collector on an estate has a certain rare item that he might be willing to trade or sell for the right price.
As I've said before Gear at Sovereign creation should subtract from your initial gold and not your character points. If character points are to be spent you should get a fairly powerful item for that sacrifice. It would be cool to have a legendary shield in the beginning of the game for 10 points or a steel broadsword for 4 points.
Now to get to the main point after all those tangents. As I said before each gear/item should have a grade with metal weapons having adjectives like bronze, iron, mastercraft, steel, vidrium, elemental Iron, Elementium, and Legendary while leather armor might just have Rawhide, Boiled, Mastercraft, Drakeskin, Dragonskin and Legendary and a Band of Strength might begin with Minor, Moderate, Arcane and Legendary. Each level would give a bonus or remove a penalty. Like the item that has the berserk quality that gives plus 3 attack and minus 3 defense might end up at the highest level giving plus 6 attack and only minus 1 for defense.
Whether you can make a specific item or not might depend on whether you have the resource or if you have crystals or an appropriate shard or the right adventure, civilization, or magic tech. Like you learn Mastercraft Warfare tech and you can then make mastercrafted items but you can only make vidrium short swords if you have a vidrium mine or a bronze short sword if you have a bronze mine.
A consequence of doing this is that if an iron shortsword only costs your soldier you're training five gold then it isn't so ridiculously expensive to equip your champions with moderately decent equipment. Most games I never buy any equipment for the majority of my champions as I don't want to risk them in combat if they're giving me a good bonus and two it can cost a fortune just to buy leathers, a shield, and a basic weapon.
But, with differing grades of gear you open up the possibility of making some really powerful champions with Midnight blades and ancient relics like Rods of Leadership granting 10 points to charisma. The costs can then go through the roof and with the above idea of limited availability and production of the rare items you end up treating them as more preciously.
If in D&D you could just go to the merchant and buy twenty vorpal swords +5 for your henchmen it would definitely hurt the flavor.
It would also be cool to have one of a kind Artifacts that can never be duplicated or items that absorbed a little of the nature of their famous master like the "Staff of Ereog" Or Morrigu's Cloak of the Raven.
