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
Segment your customers to find the diamonds in the rough
Not all customers are equal but it is difficult to dig through all of your data to find the best customers.
Repeat Customer Insights will automatically analyze your Shopify customers to find the best ones. With over 150 segments applied automatically, it gives your store the analytics power of the big stores but without requiring a data scientist on staff.