Furthermore, the price of oil has an upper limit, which is defined by the alternatives available. If it were simply impossible to duplicate the benefits of oil by other means, of course the price of oil would skyrocket out of control until every drop disappeared.
However, there are many substances/technologies which can replace oil even today, with no new innovations – they just cost more.
Once the price of energy created with oil reaches the price of alternative energy sources, some of which are only 2x more expensive, it will simply not go any higher. Even solar – currently the most expensive alternative, and certain to be come less expensive as time goes on – will keep the price of oil under $300 (I think – my wife threw out my National Geographic with relative cost info – darn it!).
My concern with oil is – how do we make plastic? This may drive the price of oil up, once oil is no longer used for energy.