When I was working on 99 smith, I too looked for the cheapest route. Unless your willing to mine all your own ores, there's only one way I found to make money from smith, unfortunately it's also one of the slowest.... making cannonballs. I was buying steel bars, making cannonballs, and coming away with a profit of around 350 to 400 per bar. I did it for several levels before I got sick of it, lol.
My next method was to buy iron bars and make iron knives out of them. I don't remember how much money I lost on that one, but it wasn't too bad. I was checking todays GE prices on iron knives -vs- iron bars and you could almost break even. One iron bar costs 306, and the 5 iron knives you would make sells for 305, so not too bad of a difference there.
The last few levels of smithing I just wanted to get it over with, so I bought Addy bars and made addy bolts, took a bit of a loss there, but it was nice and fast.
The one thing I forgot to mention is that the whole time doing iron knives and addy bars, I used the Stealing Creation hammers to speed up the xp. It really saved allot of time and money. Did the same thing for Construction, cut my costs in half.
Good luck smithing 
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But i'm kind of cheap and going the slow and cheap way ( yeah yeah, buying iron ore, smelting it into iron bar and then smithing them into iron knives.. 
(cept for herblore cause it's one of my fav skill)