Unrealized profit calculation

26.11 On 1 April 20X7 Possum Co acquired 60% of the share capital of Koala Co for $120,000. During the year Possum Co sold goods to Koala Co for $30,000, including a profit margin of 25%. 40% of these goods were still in inventory at the year end. The following extract was taken from the financial statements of Possum Co and Koala Co at 31 March 20X8. Possum Co Koala Co $’000 $’000 Revenue 750 400 Cost of sales (420) (100) Gross profit 330 300 What is the consolidated gross profit of the Possum group at 31 March 20X8? Unrealised profit (30,000 x25% x 40%) =3000 Gross profit (330 + 300 – 3)=627 Why is PUP not ( 30000 - 30000/1.25 )*40% = $2 400? Because P sold to K FOR 30 000, 30 000 is the revenue, not the cost, so why does the answer treat the 30 000 as cost by calculating the profit = 30 000 * 25%?