It's really just a trade-off between safety and freedom. We didn't spend any time in cities, so we really felt we needed wheels. Also, the cabs and buses have to use the same wild streets. They are more familiar with the Tico drivers, so they might be marginally safer.
I'll have to look up what we paid for the Rav 4 (oops, did I say 4 runner before?). I think I paid something like $700 total for 12 days last August. I think daily rates could be much higher.