Hi Kisaya,
I can't speak to pricing, but I can help you a bit with the international shipping thing without stepping on toes. These are good kilns, and I have made purchases from Sundance with good service. I also hear good things about Mountain Glass from many.
You could ask both vendors if they work with FedEx. If they do, there is a great rates program that allows us vendors to call a number and get special pricing for times that FedEx needs to fill a spot on a plane. Most of us don't know it exists. I have only known a few months.
FedEx Great Rates
The last few times I called I saved customers between 50 and 70% off the quote over and above my normal account discounts. It is a service that requires you to ship on an exact date that is dictated by FedEx. Normally within 5 days of the call to them. It seems to travel about as fast as it would on a normal shipment, but they do not guarantee the delivery date. (This week we shipped an 8lb package to Australia that originally quoted out to $198. I was able to ship for $98 on the following Monday. The heavier the box, the more savings they can give.)
I would bet UPS has a similar thing, but I am not a customer of theirs.
As far as lowering the value on the customs form, that is a policy most of us will not break. It leaves the vendor and customer stuck if anything happens in route and has to have a claim done. Kilns are a tricky shipping item. It is best to keep the customers purchase protected all the way to the destination. No one wants to take a loss.
Maybe the savings on the shipping will help balance out the import fees. Some countries tax rate on imports both shock and scare me.
Hope it all works out, nothing worse than knowing what you want but a detail is in the way.