1) I make widgets and sell them for $10.
2) The government reduces the value of my currency by 10%.
3) The market value of my widgets is the same as before, so I raise my prices to $11 and I can still sell them them because the (real) value hasn't changed.
Following this chain of reasoning means that devaluation of a currency wouldn't encourage exports, but that's not true.
An increase in the value of another currency relative to mine may allow you to buy more of MY dollars, but the market value of my goods is still the same. The only people who would notice a difference when this happens would be those holding currency and not assets. Are those people the target of currency devaluation/appreciation, or is there something wrong with my reasoning?