It will depend upon the reason and situation due to which the btc prices have fallen . If it is due to all developed countries started to ban then sooner or later other counties will join them so point in buying btc in those cases. If it has fallen due to some negative news regarding bitcoin, then will need to check if some countries do support it or not. Because if the market will still exits then yes one will buy a lot when prices do fall in anticipation of good returns in future.