Shipping costs is dependant on how you wanna ship it, as amazon
has limited shipping internationally for items, but predominantly
ships to all of usa, i use Vpost to help ship from USA to
Singapore. But within USA, as in from Amazon to the Vpost address
in USA, that's another shipping point.
As for the amazon shipping within USA, prices vary on the speed
of delivery, eg, 1day shipping, 2 day shipping, 3-5 day shipping or
5-8 days, you can check it up on Amazon, i know 5-8 tends to be
free with purchases over 100 USD i think... but i stick often with
2 day shipping for around 20 plus USD.
When the parcel gets to VpostUSA, it will be weighed and sized
up, before delivery price is stated, after payment only which will
it then be delivered to SG. So pray that Amazon keeps the box
small, and pray that the weight of your item is light.
So all in all, it's basically 2 couriers, one from
amazon(whichever courier they use, fedex/USPS, etc) and
Singpost(Vpost USA).
If you however manage to buy from other sites which offer
international shipping, then you'd save yourself alot of trouble,
problem is prices tend to be very much more expensive with such
sellers unless you know where to look, and customer
satisfaction/gurantee of item's delivery and quality may not always
necessarily be there. Eg, problems with goods and filing of claims
will be a hassle as opposed to approaching larger corporations with
such problems.