As we talked about above landed cost is one of (if not the most) important metrics to consider when vetting suppliers. But landed cost includes more than just manufacturing costs. It also includes the cost for you to ship your products from your manufacture to your warehouse, and the cost for your warehouse to ship the products to your customers. So you must think wholistically when selecting your manufacture, keeping in mind how your decision will affect other parts of your supply chain.
If you manufacture in China for example, your manufacturing costs may be lower, but you will be spending a lot on sea or air freight in order to get your product into your target markets country.
You should also consider the effect on manufacturing lead times. If you manufacture in China it will take ~30 days typically to get your products over to the European or North American markets by boat. So that means an extra 30 days where you have cash tied up and invested without generating any return.
Lastly, the warehouse you choose to store and ship your products (ie. your 3PL) will have a large effect on your landed cost. The connection between your 3PL choice and manufacturer choice are linked because the heavier/larger your product/packaging is, the more your 3PL will charge you to store and ship your product.
The decision on how big and heavy to produce your product will depend on where your 3PL is located, and what shipping rates they offer based on package size. If you are opting for a shipping from China approach (using an agent or 3PL in China) then weight will be the primary factor in your shipping costs (not volume). If you are planning to get a 3PL in the US or Europe, then volume would most likely be your main consideration to lower your 3PL storage and shipping costs.
Generally speaking, you should try to manufacturer your product in as compact and lightweight packaging as possible, while still giving it a pleasing look and good customer experience. However, like I mentioned above, there are various other factors to consider here too. Always consider your supply chain wholistically when looking at potential suppliers. Think of the pros and cons of your entire supply chain, not just the cheapest way to manufacture something.