Expenditure on labour $=Rs. 4,50,000$
So, $15\%$ of total expenditure $=Rs. 4,50,000$
Then, total $(100\%)$ of expenditure $= Rs. 4,50,000 \times \frac{100\%}{15\%} =Rs. 30,00,000$
Now, Profit $= Rs.10,00,000$
Total selling cost $= Rs.30,00,000 + 10,00,000=Rs.40,00,000.$
So, $200$ air purifier selling cost $Rs. 40,00,000$
$1$ air purifier selling cost $=\frac{Rs. 40.00,000}{200}=Rs. 20,000$