If you used the online calculator for USPS, forget what the quote was. Go to a postal office and get a direct quote. Their online calculator is wonky at best, and unusable at worst.
I've sent several items overseas over the past year, and like the others said, USPS was by FAR cheaper than anyone else. UPS was just off the chart expensive, and I was actually surprised how cheap the postal service was. As an example, I sent 5 tachometers to Germany for about $35, which seemed fairly reasonable given the current situation. The weight is a big factor, so not sure how much that played into what you got back. I would ditch the wooden box and use a sturdy cardboard box with good polystyrene or foam protection inside. You're just doubling the price with the added weight.