You'd probably have to find a cryptocurrency that has an extremely high inflation rate. There's no other way around it. So let's say initially 1 million "coins

You'd probably have to find a cryptocurrency that has an extremely high inflation rate. There's no other way around it. So let's say initially 1 million "coins" are created and people put $1 million in total in them, so each are worth $1. To keep that $1 price, you'd have to increase the amount of coins each time more people want to buy more such coins. So if new people put another $1 million into the cryptocurrency, you'd have to automatically generate another 1 million coins. So you'd maintain, roughly, that $1 per coin value. Otherwise, with any relatively finite amount of coins in a cryptocurrency, you're going to see an exponential rise in their values, as more people get interested in that cryptocurrency. It doesn't matter if you create 1 million or 1 trillion coins initially. If the inflation rate is "only" say 10% per year, but millions of dollars, and then tens of millions of dollars, and then billions of dollars are put into that cryptocurrency within a relatively short amount of time, its value is going to explode.