the way i see it, imagine just 11 million people out of the 7 Billion people decide to try bitcoin. and they are not going to invest their whole life savings of $£50k but instead they just want to dabble with $£1k (a months salary)
well for each person out of those 11 million to get 1BTC would end up costing £$1k each as there is only 11mill coins.
in reality though id say half of the coin are being hoarded and not available to be resold. so this would push the price up further to $£2k a coin, where theres only 5mill coins available for all the demand.