Cost Price / Base Price / Final Price

[webdevprojects]

Hi

I am using VM 3.0.16 and I am wanting to enter the price I purchased the product so I can calculate my profit margins. If I enter this into Cost Price it changes the Final Sale Price of the product. I read another forum about adding this as a custom database field however then I can not generate a report to show my profit margins. I'd appreciate if someone could provide some assistance on how to achieve this please?

Thanks in advance