I was never a math kingpin, but my last startup was stock market/trading related so I got to brush shoulders with some brilliant analysts.
Their advice to me is "anytime you think you want to do a simple average, you'd be better served by displaying a histogram of averages".
I think this completely applies here too since it would help you quickly see if (a) the bulk of your customers are have a low repeat price and the average is buoyed up by a few large purchases or (b) one customer orders a whole bunch of tiny items at a low price dragging the averages down.
Their advice to me is "anytime you think you want to do a simple average, you'd be better served by displaying a histogram of averages".
I think this completely applies here too since it would help you quickly see if (a) the bulk of your customers are have a low repeat price and the average is buoyed up by a few large purchases or (b) one customer orders a whole bunch of tiny items at a low price dragging the averages down.