Based on my years of experience with Amazon, all your problems will be easily solved if you simply choose a reliable freight forwarder.
I can introduce you to someone if you need it.
For me it’s usually consistency.
Sometimes the sample looks fine, but once you move to the actual order, timing, cost, or quality can feel different.
Shipping cost is part of it too, but a lot of the headache usually comes from the stuff around it, not just the quote itself.
If you can sell it, so can another 100 other sellers.
Product quality always.
Shipping cost.
Quality.
May be shipping cost