For the most part when it comes to metals in World of Warcraft, ore sells at a higher price than bars. This is not true, of course, in a direct item-to-item price comparison, but is true in terms of overall cost. In other words, some bars require more than one ore to craft so take into account how many ore it takes to craft a bar of the same material when conducting comparative pricing.
The reason is that ore generally sells for more than bars is because jewelcrafters can prospect the stacks of ore for gems. Bars, on the other hand, cannot be prospected. This mechanic means that ore has a larger potential demand pool than the demand for bars. And, as we’ve seen examples of this repeatedly in the WoW economy, this greater demand will almost always lift the price of ore over the equivalent price of bars within your server’s community. If you’re a miner in the business of selling your ore, or even if you’re just considering entering the metals market, use the knowledge of ore > bars to your full profitable advantage. There are occasional exceptions to this price disparity and even a few special cases where ore cannot be directly used to craft a bar and prices generally reflect this mechanic, but these cases would perhaps be best discussed in a separate post.
Edit: This topic was expand on further in this post.