Why cant I ask a price of total cost? I should not have to do it since I am not the seller. It the seller job not mine.
Since he is offering different price-steps and only you know which of them you will need, it should be your task to calculate the cost.
And it's not even that hard.
He wrote you need 1.800 pieces total. Therefore you could have:
1. Need for all 1.800 components and therefore pay 70k each, which would be 1.800*70.000=126.000.000
2. If you already have a complete set for one part (600 components) and want to purchase the rest of 1.200, you'd need to pay 75k per piece, which would here be 1.200*75.000=90.000.000
3. If you're just missing maybe 200 components you'd have to pay the highest price at 80k per piece, therefore 200*80.000=16.000.000
Notice: Option 2 and 3 can be combined with "x*600*75.000 + y*80.000 = complete price"