When you ship internationally there are a few things to consider.

First, you have to accurately describe and categorize the stuff you are sending. If you list an incorrect harmonized tariff code your delivery might get returned or stuck. This happened to me recently drop shipping to Canada when my supplier sent fiber optic cables but used the code for copper cables. Little mistakes become big problems with import/export.

I don't think anyone here has to worry about defense items, so we can skip that nightmare.

Next, there are duties/tariffs/VATs that have to be paid. These are either going to be backcharged to YOU the shipper, or will be charged to to recipient. These are based on the category of the goods as well as the value (which is why a full commercial invoice is required). I never, ever pay those (learned my lesson) and ship everything DDU (deliver duty unpaid). Sometimes you need to get the tax ID of the recipient and put that into the shipping docs. That is how it works for me when I *import* things - I will pay my supplier for the goods and for the shipping cost, then later I will get a bill from DHL for the duties and brokerage fees. This is normal, and I expect it. Your customers should also expect it - no way should you as the vendor and shipper be on the hook for those charges.

Finally, there are broker fees. The fees from DHL seem to be the most reasonable. These, also, you cannot escape, and should be the responsibility of the recipient. You can ask to have these estimated, but do not guarantee the final cost to the customer. They are the ones *importing* and that always comes with some risk and uncertainty.

The last thing I will mention is that if you ship regularly and/or are shipping to some esoteric country, you should check to see if a freight forwarder might be more economical. I used them for shipments to Sweden and Trinidad and they made were easier and cheaper than Fedex/UPS/DHL and have must better customer service and will be responsible for delivery to the final destination.

(edited to add)

If your customer asks you to send a doctored up invoice that shows the sale for less money so that they will pay less duty, DO NOT DO IT. You are signing your name to a legal document when you fill out the export forms. Do not write that you are sending gifts or some other nonsense. Be safe about it - Uncle Sam don't play.