You forgot to mention what you are looking for, besides an economic place to visit, are you looking to surf?, to hike?, to relax? to visit a volcano? that makes the recommendations more vague. Costa Rica is a beautiful country you have adventure and relax anywhere in the country. What is cheap and expensive? that is up on your budget and the season you choose to travel. On the Pacific Coast, one of the most visited beaches, Santa Teresa has hostels for $15 the night in high season...and almost for $10 in low season. It has great waves to surf and to swim, it has a wide variety of restaurants and accomodations and plenty outfitters activities to do. However, if we are comparing Santa Teresa, Costa Rica with San Juan del Sur, Nicaragua what i can say is that San Juan del Sur is cheaper, the food, the hotels, rentals and It has great beaches.

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Central America and Mexico Travel Forum
Central America and Mexico Travel Talk

Costa Rica is not as cheap as before. If you want a cheap country, you should stick to Central America, especially Honduras, Nicaragua and El Salvador