This sounds interesting enough, but it is just forex with a different exchange medium. It still follows the same logic and concepts of forex, but the pipe that the water flows through is a bit different. All of the same understandings would be there, the ability to predict, etc, but it is just forex at the end of the day.
Like others have already said, for this to work there would have have to be a massive swing in the rate in a short space of time, and even if it did happen then with the commission they factor in, I doubt you'd be able to make a lot of money doing it this way. If it's worked you then good luck, but I doubt it's a reliable way to make money in the long term.
You could do that with South African Rand maybe. I know a person who recently bought $500 for a planned trip to the US, the trip was cancelled and he got back more Rand than when he started, despite the fairly large margin. Maybe you could do it buying Dollars with Roubles too.
I am not sure if it is as really as easy as you make it seem, at least I would assume not. Like other users have said also, if it were lucrative and a good way to make money, then people would be flocking to it like it was nothing so the fact that that isn't happening might certainly tell you something. I am interested now as to what really deters people from doing something like this.
I think that, given a relatively small transaction fee, you hast have to time the market and be able to invest whenever there is a significant drop.
Like everyone else I've kept hold of currency after business trips and exchanged it when the rate is better. I have considered doing this for income, but the margins taken by the exchange offices are sizable and seemed prohibitive. For me it would require a substantial shift in the exchange rate, or a very large investment, to make enough to be worthwhile, and there were safer alternatives. However, with a good exchange bureau which offers low margins, there's no reason it shouldn't work. However, assuming you aren't using a multi-currency account and trading online, you'd not only get a better rate through a specialised forex trader, they would also have the advantage of not handling large amounts of cash or cheques in whichever currency you are trading. That really doesn't seem safe.
