Many stores spend a lot of resources on customer acquisition.
How much does it cost on average? What about an online store customer vs POS vs Facebook? Does it increase over time or stay within a band of costs?
But acquisition costs are only part of the picture. You'll want to look past the first order and see what are the total costs of retaining customers.
The costs to keep a customer are much lower but I think that's part of the problem. Shopify stores aren't spending enough resources to keep customers so they, like most ecommerce stores, lose the majority of customers after the first order (industry figures put the loss around 3 customers out of every 4).
It makes me wonder what customer retention would look like if a store put an equal amount of resources into repeat customers as they do new customers. They'd probably do so well that they'd hide that strategy from competitors.
A quick way to measure how well your store does is to use the Repeat Purchase Rate (RPR). A best one is to use the per-order interval (customer's second order vs third order, etc). Repeat Customer Insights calculates these automatically and will even compare it to industry norms and your historic performance.
If it's lower than 25%, you have more than 3 out of every 4 customers leaving and never coming back.