[lottin]

Your analysis is incorrect. Markup is a function of market power. If market power remains the same, an increase in markup cannot last for long. Competition will drive prices down until markup goes back to its previous level. Therefore the end result is a fall in the price of exports. Whereas for importers the opposite is true, imports become more expensive for local purchasers. This is what is meant by "selling cheap and buying expensive", which is exactly what happens when a currency depreciates.