I think the more recent note is
SAP Note 876617, which explains the condition technique of SAP and which possibility their is to go around it. Exactly the same thing as Mr. Vivek Sahni, but of course without the concrete program code, which is of course much helpfull in this case!
Also SAP Note 1758118 give another solution from a more transportation wise thinking, transport costs differ mostly per weight amount.
In my short experience a service material "Freight cost" is created, linked to first of last item of an sales orders, delivery relevant, so it can only be delivered together with first or last material of sales order and thus only be invoiced once.
This freight cost service material must be printed as footer on invoice, seperate subtotal, so output program invoice must have added logic for this.
And in pricing set up, if needed a different pricing table, with material in it, can create the correct pricing (with scales etc) as needed.