Is TWS overpaying DHL?

I just ordered another case of kombucha (I know) from TWS and took deliver. Interestingly both the tracking info on DHL and the label on the box said that the package was 16 kg. Having measured the weight of a single bottle (542g), the weight of a box is between 6 and 7 kg. Is it possible that DHL charge is impacted by weight and if so has TWS been ‘ripped off’ in this instance?

Most companies with contracts with couriers like TWS (and my own company) have a fixed price for all deliveries up to a certain weight. Typically that will be the weight (for charging purposes) put on the label. So all our deliveries up to something like 20kg (I think) are one fixed price and so long as a single delivery (not parcel) is less than that we get charged the same price* and I’d guess TWS have a similar set up based on the typical weight of, maybe, a case of 12 typical bottles. And that is maybe the 16kg.

*And, incidentally, if you’re wondering how much you get ripped off with delivery charges; we aren’t that big but we only pay £9.50 up to 20kg anywhere in the country (including the highlands!!!).