If other countries (like El Salvador) are using our currency, why don't they go based on our inflation rate? For instance, the price of a grande Starbucks drink in El Salvador was about $3 where ours is like $6 or so.
Lots of other things are important when determining price - supply, demand, the cost of producing the good in El Salvador vs here. I wonder if the coffee is even the same or if they use cheaper ingredients. I imagine the willingness to pay here in the US is higher since we are, on average, wealthier.