Hey there,
is it possible to buy BTC cheaply at one exchange and sell it more expensive at another one? It seems to me that it might be actually possible.
What are challenges? Are people doing this?
Yes, it is certainly possible
But the major issue with what you are aiming at, it is not just about Bitcoin. More often than not all currencies at a certain exchange are traded at a premium there. This basically means that it is a one way road mostly, i.e. you can buy bitcoins cheaper at one exchange and you can sell them dearer at another, but you won't be able to move funds between these two exchanges cheap enough to make arbitrage economically feasible on a regular basis. What really makes arbitrage possible are random price spikes and dumps when someone sells or buys big time