So you've decided NOT to ship a container (personally I think that's a WISE decision usually. More on that later) and you're looking around trying to find things (Where? More on that later also).
"WHY ARE USED THINGS OFTEN SO EXPENSIVE IN COSTA RICA?"
I find that Quality, Uniqueness and Price Paid often contributes a higher price ESPECIALLY because it's not always easy to get QUALITY things here in Costa Rica - unless it was brought from abroad - so then you have shipping expenses to factor in. A LOT (NOT all) of the cheaper used things I've seen in Costa Rica - say on CostaRica.en.craigslist.org - haven't always good/longer lasting quality.