Personally I would prefer the lowest possible price rather than any of the three options. If its the lowest price it will generally get the most business with the odd exception.
The reason I say this is because I have customs to contend with. When the value is $150 I pay between 45 and 50 in duty. Approximately 33-40% depending on how the Customs Official classifies it, so the lower the cost, the lower the duty, the easier on the pocket.
That said, if I was in the States I would have answered the "thank you gift". The odd little surprise is always nice but heres a suggestion...
How about allowing customers to choose their gift - ie. if spending between 50 and 100 you can have one out of these possible choices, 101 to 150 pick two out of the following choices etc. Perhaps create a seperate gift page with codes to enter at checkout.
This is a fantastic point that I never considered. The free item kind of loses its luster when you have to come further out of pocket to pay customs for it. Maybe an "Over Seas Friend Discount" could be considered instead of a freebie. As far as pick your gift I feel that takes away from the sellers generosity and becomes an entitlement. I like when I am packing blanks and I look over and just grab a random burl to toss in and fill a void.
I think 100% it is the sellers choice as it is their expense. That said they could send a message to Over Seas Orders and say, "Hey, I was going to toss some freebies in there, would you prefer that or a discount"
Other than that I see is as my girls say it. "You get what you get and you dont throw a fit"