There's a simple test for your spreadsheet model. Plug in $7500 tonne product value and 10% discount rate, and you should get RPA's numbers for NPV and IRR, more or less. I can guarantee that you won't.
You were wrong with your guarantee statement, why should anyone believe anything else you say?
I said "more or less". The issue was precision. You weren't within my generous allowance of 5%, plus or minus. I didn't assume directionality at all.
Because you have so many errors, you can't tell what effect those errors will have when you change your input numbers. GIGO.
If you can't validate your spreadsheet on first priciples, it cannot be relied on at all.
Lar