Upload & Sell: Off
I'm not defending anyone here, but I'm surprised at the number who would simply brush off income that was legally contracted to be in your pocket, regardless of what kind of work had been performed. What if 8 of your couples just up and cancelled...you're out potentially $17k of your yearly revenue (assuming the balances owed were only around $2100).
Sure it sounds crazy to think you should still keep that money, but you signed a contract (not just them) that agreed to specific terms and conditions...and you were committing your services to particular person with the knowledge that you would forgo contractually obligating yourself to another full-paying customer. Why should you be out your promised income because they decided they no longer want to fulfill their end of the deal? It's their choice to not use your services on that specific day. Just because they don't take advantage of a "pre-paid" photoshoot doesn't mean you should refund their money.
I can understand that some might think we are not "entitled" to that income because our work is predominantly service based, but we are in fact "entitled" to that income because they agreed to pay when signing a contract. Just because you haven't arrived at the venue to perform your services does NOT mean you were not willing to fulfill your obligations in the contract. Refunds for unfulfilled balances seem appropriate to refund only after the date has been rebooked.
I'm not saying I would follow through with it, because I've never had it happen. But why should you suffer the penalties of another and your family has less food, less college funds, less whatever, because you decided to go in to business with someone that would end up flaking on you?
If the OP didn't offer to fulfill his end of the bargain and deliver an equivalent value of services, then that is definitely a problem.