If I farm the materials to make it, it's 100% profitSomeone used this the other day to justify selling his Avenger's Trillium Legplates for 3k. After I bought them, I questioned him as to why they were so cheap. The materials alone cost 3k to make.
First thing, farming takes time. This is time you could spend doing other things, and that's why the price of rarer materials that are harder to farm are higher.
Second, if you farm all the materials to make something rare like the legplates you should probably sell them at a higher price. You are severely undercutting people who literally just buy the materials to make it. You are putting in 100 times the effort for 1/4 of the price.
Third, I will take advantage of your prices if you do this and resell at the normal price. Then I have put in literally no effort to buy an item you spent a month to make, plus your farming time, and I can resell it to get three times the profit.
Farming items does not equal 100% profit!