I imagine Square would want the devices in as many hands as possible that actually accept credit card payments. If Apple retail stores were to simply give away

I imagine Square would want the devices in as many hands as possible that actually accept credit card payments. If Apple retail stores were to simply give away the devices, there'd be a lot of people picking them up, with little advantage to Square. People like free stuff, even if they don't know what to do with it. By selling the product for $10, customers will think it is at least worth $10. On Square's website, it's fine to give the devices away, because many of those visitors are already interested in accepting credit card payments. Not all Apple retail store customers are. On every Square sale that Apple does, Square is probably out $5 or more, but it's worth it, because it weeds out the least serious customers.