I use a Macbook Pro which works in NZ using just a plug adapter but I'm not sure if all laptops are this way. Ditto with many hairdryers - if there's a switch on the handle to change from U.S. 115 to NZ 240 but you'll need a plug adapter. I just bought a bag of 15 US to NZ plus adapters for $1 each! I'm not taking any American electrical appliances to NZ but will buy new when I get there rather than fool around with transformers, etc. which may not work if the appliance has a motor.
The basic cheap appliances (toaster, tea kettle, etc) can be bought at Warehouse cheaply for not much more than what you would pay at Target - but better quality appliances will cost more than the U.S.
U.S. Breadmaker = $80. NZ Breadmaker = $150 (on sale). I'll buy the basic appliances cheaply then upgrade when they need replacing. There's no such thing in NZ as a cheap vacuum - and I have yet to see an upright. Expect to pay at least $300 for a cheapie canister type vacuum. NZ washers and dryers are smaller and cost more....plus most Kiwis hang their clothes on the line out of preference, not need. But I've recently priced washer/dryers on sale at a comparable price to what you'd pay in the U.S. Refrigerators have also come down in price and larger ones U.S. types are easier to find. I plan on buying my major appliances from the same shop so that I have some bargaining power.
My brother in law uses his Kindle in NZ - guessing that he just needed a plug adapter.
A good place to price things is:
www.priceme.co.nz