The formula is a rather complicated manner to calculate the tiered cost. The first VLOOKUP finds 215000, i.e the cost for 20 ads. The next part evaluates to the number 2, being 22 (F6) + 1 - 21 (the result of the second VLOOKUP). And the last VLOOKUP returns 9000.
The end result becomes:
215000 + ( 2 * 9000 ) = 233000
In the attached file, I have given an example of you can achieve the same result in a different manner.