I thought of this as well (happy customer) but the economics are a bit different: My understanding is that Canada Post absorbs the cost of mailing keys to the War Amps as a deal it makes to support this charity. I also guess that War Amps pays the cost of actually returning the keys and yet comes out ahead, based on expected rates of keys being lost and found (though perhaps Canada Post subsidizes this part as well).

This service is going to have to cover that cost as well as the cost of returning the lost item.