A company is considering to purchase a supplier for $2M, expecting to save $500K annually for 10 years. My calculation of NPV and IRR (21%) showed the purchase will be profitable and payback period is 4 years.

1.Is there minimum amount of savings that a company is expecting to get from the investment that will make the investment still attractive and will make the purchase possible?

2. If it is less than the the $500,00 expected savings, will it still be attractive. I made some calculations, andwondering if a 0 NPV is really acceptable. Interpretation of NPV seems to be too good and I can't find an article proving that NPV of 0 is an indication that acquiring this supplier is a good investment. So, no savings ( or as long as it's not a negative) will still indicate that buying the supplier is still a good investment????

3.Could you please include references?