Pfff... you may return it to sender, but good luck getting a refund this way. A better option, I think, is to sell it (albeit a bit cheaper) quickly to someone who is willing to also pay the customs tax. But still, you should wait until you get the invoice from UPS, you may just slip through 
For anyone else receiving this kind of equipment from overseas (doesn't matter in which direction)- most companies can't estimate what you would pay in customs for your units. I had this exact situation last year when receiving from BFL, I had to pay customs for my order when coming from US to EU. Since each country has very, and I mean very complex customs laws, it's more or less unpredictable for businesses even if they are willing to give you an exact quote. And don't even get me started on shipments from China... Depending on where you are, you can pay from nothing to 200% import tax... So always keep this one in mind
For anyone else receiving this kind of equipment from overseas (doesn't matter in which direction)- most companies can't estimate what you would pay in customs for your units. I had this exact situation last year when receiving from BFL, I had to pay customs for my order when coming from US to EU. Since each country has very, and I mean very complex customs laws, it's more or less unpredictable for businesses even if they are willing to give you an exact quote. And don't even get me started on shipments from China... Depending on where you are, you can pay from nothing to 200% import tax... So always keep this one in mind
I buy stuff from Ebay all the time, even from places in the states that are the farthest from me. It just depends on how the sender sends the items, they can send with the full price value or they can mark it down. Most companies in the US who sell stuff over the internet either mark the price down or charge you the tax, if they charge you tax it costs you nothing when it gets to your door.
So really it depends on the company who's sending it.
Unfortunately I can't recoup the $12k plus the $2100 for duty and taxes and I am not about to take a loss on a brand new product, so I will take the risk. I have already informed KNC Miner so they are aware and kept in the loop.