Looks like you'll have to nest IF statements, but at least you'll be able to copy/paste the formula into every cell once it's written:
=IF(A1<=5,"400000",IF(A1<=9,"600000",IF(A1<=11,"80 0000",IF(A1<=14,"1000000",IF(A1>14,"1200000")))))
Pretty sure the above, converted to "normal English", means "If A1 is less than or equal to 5, then set value as 400000; else if A1 is than or equal to 9, set value to 600000, and so on...
Have that to work out the drilling cost, then use =SUM(B1+3000000) for the total cost.
The above assumes your rock thickness values are in the A-column and you're outputting drilling cost to the B-column; change those cell-addresses accordingly, paste the two formulae into the relevant columns!
It's been a while since I did any excel-formulae-programming, but I "think" that should work...