Watch this video to start:
25% Cost of Delivery
25% Cost of Acquisition
BUT if you want profit, this view can quickly find where it is getting eaten up.
A few general rules developed from viewing hundreds of P&L's...
COD is on average around 40%. Pressing that down in every imaginable way is the biggest unearthed area of savings.
profit greater than 15% puts you in the top 5%.