Have a value 2100 want to mutiply first 75 x6 then up to 1000 x4 then over 1000 x3

Assuming your value of 2,100 is in cell A1 then this should work ...=IF(A1<=75,A1*6,75*6+IF(A1<=1000,MAX(0,A1-75)*4,925*4)+MAX(0,A1-1000)*3)