Shipping from USA (Tallinn)

I have some personal stuff like clothes, guitar, etc that I had to leave in storage in the US until I got settled here in Tallinn. Now I need it shipped over.

DHL, UPS, FedEx, etc all quoted $ Protected content box (12x12x16; ~ 15kilos each), and that seems ridiculously expensive.. Container companies I've spoken to won't handle personal items at all. There's nothing large like furniture or vehicles..

How did you get your stuff here from the states that you couldn't take on the plane when you flew over?