You must not have sent stuff over here yet or you would know how costly it is to do so. Don't even mention using fed ex or ups for mailing things. USPS is much much cheaper of course. They have a flat rate box that you can use to send up to 20lbs for 50 bucks. The boxes measure 12 x 12 x 5.5. They don't hold much at all. The other shipping companies charge about three times that rate. Depending on the size of your boxes, you'd probably be much better off sending them via shared container by sea. Several others here have gone that route with good results, myself included.
Oh, I wish they'd told me about the 20lbs for $50 when I shipped some things in August - I had to pay $200 for two small boxes (total weight about $45lb) because the USPS guy said that the flat rate boxes had to be 4lb or less in weight!
I shipped those two small boxes and a bicycle from the US to the UK and it cost me over $400. Had I shipped them with UPS or FedEx, it would have cost about $1,000 for the bicycle alone

! The main problem I had with shipping was that USPS have stopped ground shipping now, so rather than paying much less and waiting 6 weeks for my stuff to be shipped by sea, I had to pay almost double the price for 6-10 day airmail shipping

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Has anyone lately priced taking a box or two along as cargo on the plane? I'll have a cat in haulage already.
I would imagine that the box(es) will be subject to excess baggage charges, which from my research when I was considering taking my bike on the plane, is around $125-$150 per extra item up to a certain number of items, as long as each one does not exceed a certain weight.