Cost calculation from Bottomup

It would be easier if you could open the excels and PBI files.

So what is happening is, when I am looking at the cost at month level the number is ok. System is pulling sales Quantity at monthly level and multiplying the monthly cost from another table which is linked.

However when I am looking at the sum or looking at data at quarter level using drilldown option, PBI is not calculating the cost from bottom up, rather its summing the cost and doing the calculation.

Below example will clarify.

Cost of Jan is 10 * Vol of Jan is 20 = 200 

Cost of Feb is 11 * Vol 30 = 330

Cost of Mar is 10 * Vol 30 = 300

Hence the Quarter cost should be = 200+330+300 = 830

But when I am using drilldown the result is = (10+11+10) * (20+30+30) =  2480.

The cost is getting calculated incorrectly.