For repeat customer performance, Profit from repeat customers is the best metric to watch.
Being based on profit, it's a core business metric. Direct costs to acquire repeat customers will tend to be lower than new customers. Indirect costs could be higher as repeat customers could use a greater portion of overhead costs as your loyalty, retention, and other programs are long-lived before you see a repeat order.
You'll know the process is working well as long as it's positive, trending up, and a good enough business return.
If costs are difficult to separate and calculate for repeat customers, revenue from repeat customers is a good alternative. As long as you watch your expenses and margin, segmenting your revenue into new/repeat customer can show you the health of your business as a whole.
Eric Davis
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If you'd like to have your customers analyzed, segmented, and then explore specific advice on how to build their loyalty, Repeat Customer Insights can do all of that for you.