I assume that the thing (whatever is it) is divided into two equal tons. One is work 10 and one is 8.

Intotal we have, (if x is amount for half-amount).

10x+8x=728

18x=728

x=40.44

Then the full amount is 2x (because we considered half-amount).

2x=80.88 tons

The average amount being paid is:

PRICE/QUANTITY.

The price is 728 and the Quantity is 80.88

Thus,

728/80.88=9.000

Thus it is 9 dollars.