> The spending power issue could be ignored as "without loss of generality"
Great! Then you will have no problem accepting the following offer: you give me $1000 today, I will give you an arbitrary amount of money that you get to specify (so it has to be computable -- no busy beavers allowed). The catch is that I get to specify when the payout happens (of course with the same proviso: the payout will happen after a computable amount of time).
Well, no. This game sucks for individuals. That's not the point though. The point is that even though the game sucks, this is the game that represents the economic reality. And while this tweak of you or somebody deciding when to pay is a real part of the game, it is still a markov process that will result in the same wealth distribution due to the law of large numbers and people settling at the endpoints all the time, no matter how delayed in time or how small the chance.
> this is the game that represents the economic reality
No, it isn't. Economic reality is nothing like flipping coins, neither for individuals, nor in the aggregate, except insofar as both contain a random element.
> it is still a markov process
So what? Saying "it's a Markov process" is simply making the observation that there is a random element. Yes, flipping coins has a random element, and yes, the market has a random element. It does not follow that flipping coins is a good model of the market. On this logic, coin-flipping would be a "good model" of any non-deterministic process.
The interesting thing about Markov processes is not that they contain random elements. The interesting thing about Markov processes is that you can make reliable predictions about some of them despite the fact that they contain random elements. But coin-flipping is not one of those processes about which interesting predictions can be made. The economy is.
I keep saying Markov process because it encodes any kind of chance over time on a large scale. It encodes how smart the entrepreneurs and investors are born, how many opportunities they get per time step, how corrupt the regulators are, how the competition will interfere. There are real averages in numerical terms for all of these parameters that can be used. A coin flip can represent an arbitrary model if you tweak the time lags and the payouts. And if the game is large enough you can fix the payouts and extend the lags until you hit your desired fixed payouts. Coin flipping on a large scale can capture almost any economic model.
Great! Then you will have no problem accepting the following offer: you give me $1000 today, I will give you an arbitrary amount of money that you get to specify (so it has to be computable -- no busy beavers allowed). The catch is that I get to specify when the payout happens (of course with the same proviso: the payout will happen after a computable amount of time).