Not really sure what your complaint is here.
If you are buying materials from the GTN to make consumables for personal use you should expect to pay through the nose. Materials prices are always higher on the GTN than they are gathering them yourself due to the demand players leveling crafting put on materials.
Crafted items nearly always sell for prices cheaper than the components themselves would sell for due to material demand.
It comes down to a few things, mostly whether or not you want credits instead of consumables you can use in WZ's and whether or not you really need those consumables in WZ's. Also, it seems like you expect to make a credit profit from WZ's. In my experience, PvP is a credit loss which is made up for by other rewards that credits can't get you.
It seems like your outlook on WZ's is a bit skewed.
I'm sorry, but you have a misunderstanding of basic economics. If you gather materials out in the world, they are not 'free.' There is an opportunity cost. If you *could have* sold them on the GTN for a certain amount, that is their value. Thus, it does not matter how he acquires those mats. The cost associated with making an item is based inherently on the opportunity cost of the requisite materials.
The OP's concern is a legitimate one. The effective cost (and I'm sure it varies wildly from server to server) of consumables is very, very high.