If nested formulas, get "too many arguments" error

I'm building a formula so that it will calculate royalties to be paid to an investor as follows: i) Royalties are capped at 5 million (will not pay royalties after revenue exceeds 5 million); ii) Royalty on 4th and 5th million is 2%, on 3rd Million is 4%, on 2nd million is 6%, on 1st million is 8% (i.e. on the 1st Million of Revenue). The Revenue value calculated by the spreadsheet is on cell $G$13.

The formula that is getting me the "TOO MANY ARGUMENTS" error message is:

=IF($G$13>5000000,((2000000*0.02)+(1000000*0.04)+(1000000*0.06)+(1000000*0.08)),IF($G$13>3000000,(($G$13-3000000)*0.02)+(1000000*0.04)+(1000000*0.06)+(1000000*0.08)),IF($G$13>2000000,(($G$13-2000000)*0.04)+(1000000*0.06)+(1000000*0.08)),IF($G$13<1000000,(($G$13-1000000)*0.06)+(1000000*0.08)))

Please help me out! I really need a solution as soon as possible.

Thanks!