Another thing to consider when selling honey by weight vs volume is: When selling honey by weight, you have such a huge variety of containers in all shapes & sizes. It would be impossible to estimate the volume of each & every container you could possibly put honey into.
You simply put whatever container you like on the scales, tare it off & away you go.
Hi Jape, I sell honey by the bucket. However, the honey is always weighed. Some people bring 20 liter buckets for me to fill, some want their bucket filled, which will hold 30 kilos. Others want 27 or 28 kilos in them. Some want me to take the honey up to a certain final price.
Ten liter buckets are an ideal size & easier to carry. Even with 15 kilos of honey in them, itâs hard to not weigh it because you donât want to rob yourself OR the customer.
You can always go over, but you canât come under. This is why weighing the honey is so important. To make sure your not under weight, or under volume.
Jape, stop it, your making me feel hungry.
Not sure what wasnât helpful. A quick google fu reveals that the requirement in your country is also by weight; http://www.waas.org.au/docs/Labels.pdf
Itâs the same in the US. Regulations require net WEIGHT on labeling.
(US) Basic Labeling Requirements;
LABELS MUST COMMUNICATE THE FOLLOWING:
The âCommonâ Name of the Product
The word âhoneyâ must be visible on the label. The name of a plant or blossom may be used if it is the primary floral source for the honey. Honey must be labeled with its common or usual name on the front of your package. (i.e. âHoneyâ or âClover Honeyâ)
Net Weight
The net weight of your product (excluding packaging), both in pounds/ounces and in metric weight (g) must be included in the lower third of your front label panel in easy-to-read type. (i.e. Net Wt. 16 oz. (454 g)) When determining net weight, use the government conversion factor of 1 ounce (oz) = 28.3495 grams or 1 pound (lb.) = 453.592 grams. Round after making the calculation â not before. Use no more than three digits after the decimal point on the package. One may round down the final weight to avoid overstating the contents. When rounding, use typical mathematical rounding rules.
Ingredients
Single ingredient products (such as honey) do not have to name that single ingredient when already used in the common or usual name on the front panel. However, if there are ingredients other than honey, you must list them in an ingredient statement. Some exceptions are spices, flavorings and incidental additives (additives which have no functional role and with minimal presence in the finished product) which have special rules.
The type size for ingredient listings must be no less than 1/16th inch as measured by the small letter âoâ or by the large letter âOâ if all caps are used in the declaration. There are exemptions that allow smaller type sizes for small packages.
Contact Information
The label must let consumers know who put the product on the market and how to contact that person. The name and the address of the manufacturer, packer or distributor of a packaged food product are required to appear on the label of the packaged food. This information, sometimes referred to as the âsignature line,â must appear on the front label panel or the information panel. If space permits, include full address and telephone number. The information must be in a type size that is at least 1/16th inch tall
liquid volumes change with temperature. Weight does not vary with temperature.Of course you also need to know the water content of a water based liquid.
I think, I have the answer.
Honey is hygroscopic, it can absorb moisture like a dry towel can absorb water, when the bottle is opened, the volume of honey can be changed according to the humidity of the air at the time. So that, the volume can vary.
Volume can be increased/decreased when there is small bubbles in the honey after harvest and when its container shaken, especially in light honey such as stingless bee honey from my country (Malaysia)
Volume can also be increased when yeast ferments in raw honey especially in light honey.
your calculation is wrong 350 ml = 350 grams
Your numbers are only true for something with a density of 1, like water. Honey has a much higher density than water, so @Rodderickâs numbers are actually correct. 
What I interpret Rod to be saying is: You can fit 500gm of honey into a jar that would normally hold 350mls of water.
Honey is almost 50% heavier by volume than water. As @Dawn_SD said âa density of 1, like waterâ.
1 kg of water = 1 liter of water, Iâm guessing at room temp. & at sea level.