Oil is a renewable source but we use faster than it renews so it might as well be non-renewable if you get what i mean.
Also, prices are determined by how much we are willing to pay for it and since we all need it then we are always going to pay for it. Just like cigarettes are for smokers, they 'need' them so they are always going to pay for them no matter what the price.
Another factor for the price is since we are running out, companies are trying to get the most out of whats left to make as much money as they can. And since we need it, we keep buying. Its a vicious circle