Hi Terry,
The short answer is that the tax is different for every item. But when calculating what to tax they take into account the value of item, the freight cost and the insurance cost.
This is a great website with a detailed breakdown of this: http://www.costaricalaw.com/customs_law/taximport.php
My best advice is to hire a broker based in Costa Rica to help you bring in your household goods – NOT a moving company in the U.S. The CR-based folks know the local rules and regulations and can help you value items appropriately and reduce your costs. Barry Wilson at ShipCostaRica.com has spoken at IL events and has many years experience. Visit that website and you’ll find his contact info – mention that Jason at International Living sent you.
Containers go to the port in Limon, on the Caribbean coast. That is where the taxes are paid, goods inspected. A broker like Barry would handle that process for you – no need to go yourself. Then you’d have a truck take your stuff over to Coco.