Letter postage really ticks me off, lol

A lot of my items are individually under 50g so can be posted for max. $3 to an international destination. As soon as the letter weighs 51g (up to 250g), it's $9. That's ok if I'm posting 10 items together, obviously, but I can hardly charge $3 P&H for one item and $6 for a second item.  In the shop where I offer international postage, unless I start postage prices at $9 (which I don't want to, for numerous reasons), I have to take into consideration how much I can offer so that on most occasions 2-3 items still comes under 50g, ultimately resulting in worse value for money than I could otherwise provide on item costs. 

One of the reasons I don't get it, is that it would increase the number of individual packages being sent overseas, and aside from the sheer waste of resources that causes, the terminal dues Australia Post receive is in direct relation to the difference in volume of packages between two countries, so their pricing not only actively works to reduce the postage people are paying by sending smaller, individual packages, it also decreases the money they could get via the UPU agreement.