I'm sorry but you're getting it wrong, the way I see it, Bitcoin is not really limited like people think. Every single day there are lots of people buying and selling Bitcoin and it's never going to stop. And when the demand for it gets high the price will as well be high, which means that it reduces the amount that people are able to purchase with a particular amount. If you can buy 1 btc with $1 and there happens to be a high demand, then 1 btc will start selling at $2 and that means that you will no longer be able to get up to 1 btc with that amount and will have to opt for 0.5 btc. You see?