Yes, the charges are also a guess - well, shipping can be calculated, but I was charged a couple of hundred for buying a storage server from the US once - they deemed it a stereo amplifier. Couldn't argue, coughed up. The 300 for the jackplug (YES, A FRIGGIN' JACK PLUG) was the biscuit, I'm being more careful now. If I understand you correctly, no import tariffs in the US currently then?
The thing is, I'd need "most" of the parts for the amp. Apart from some caps, resistors, pots and maybe valve sockets I'm missing most of it. If you can't order them as a kit, you end up paying a lot more, plus often I'd have to order from outside the EU (think Modulus, UK) and I get farked again. When ordering from the UK, about 50% of the time stuff actually gets here and about half of those instances come with a hefty import tax for a fictiously generated value.
I wouldn't kick myself for buying or building a clone, but I would kick myself for that if it worked out more expensive than the real deal, you know?