Instead of using text, why not simply using decimals?

=IF(C8<=1250000,0.8,IF(C8<=2000000,0.75,IF(C8<=2857100,0.7,IF(C8<=4615300,0.65))))

Then the equation is as simple as C8*B9.


Better yet, you can build a table to reference and make adjusting the parameters much much simpler. Also allows for a greater number of them.