This is a great question and something I think we should look at addressing within Mautic.
There are a number of thoughts around this, nothing out of the box or plugin which would be great.
Some things that I think of are using either google analytics goals or matomy with utm terms attached to mailers in order to better attribute sales/revenue to a specific communication.
Interesting to see what others are thinking and how they are attributing the performance or efforts inside Mautic to actual revenue