Armor and protective gear is more expensive by nature, specially the good ones, weapons are generally cheaper unless they are of mass destruction.
Prices (and everything) need to be justified, they need to grounded into proper game mechanics, and it's not really that complicated.
My opinion is that
there should be an established connection between cost to produce and cost for the buyer. Cost to produce should take into account the availability and price of necessary materials, tools, time, expertise... E.g.: Better, stronger, rarer steel, of higher price + man with tools and expertise to work with it = better stats = higher cost; The same should happen for siege weapons, they should be expensive to build, they require tons of materials, man power and expertise...
People here a talking about locking items according to level as an alternative/increment to fix prices ... artificial restriction of gear and gameplay is not a game feature that should be encouraged
(devs might be reading and they instantly go for the quick fix), other games are moving in the opposite direction, assassins creed for example.
Some high tier weapons, armor... could be considered items of prestige and require other stuff besides money.
E.g: influence; special access to even smell the gear (royal armory); connection and good relations with nobles; special favors to the blacksmith = you could smell and buy on item even though you don't have the prestige to own it...
The bigger problem that I don't see discussion on is that
there is no cost of ownership. A simplified
maintenance mechanic could be introduced. Low tier items require less money, materials, expertise to maintain and
as the tier goes up maintenance price increases.
The curve could look something like this: (yy- price; xx- tier)
Items would slightly go down in stats and value until items are fixed. Items would have durability and get damaged over time and when used. Maintenance could be done by one more party members with expertise, blacksmiths or similar. It could be automatic and/or manual. It's mostly UI work, I don't think it would require that much testing, at the end of the day if you drop the price of initial cost but have a more or less fixed ownership cost you would end up more or less at the same level and it's mostly a mechanic for the player, bots could use a lighter version of this.
This would also solve part of the problem of money accumulation at mid and late end game, even more if the concept of "cost of ownership" is applied in other circumstances.