You say you're getting 12 eggs from 15 hens and think that's somehow off, but honestly that sounds about right for healthy birds in good condition. I've kept chickens for years and found that when they're fed a balanced layer feed with plenty of protein and calcium, they'll often hit 80-90% production. 12 out of 15 is basically 80%, which is perfectly normal for a young, well-cared for flock. The real question is whether you're counting carefully. Some folks accidentally count the same egg twice if they don't mark them or if the hens lay in different spots. Also, if you've got a mixed age group, the younger ones might just be hitting their peak. I'd say enjoy it while it lasts because production usually drops off after a few months.

My friend Sarah did the EXACT same thing with giant bags of dog food. She was so excited about the huge 40 pound bag at the warehouse store, figured it was such a deal. Then her dog got sick and she had to switch brands, and she realized the per-pound cost was actually HIGHER than the smaller bags at the regular pet store. She was FURIOUS when she did the math, especially since she had to haul that massive bag home and it barely fit in her trunk. It's a total trick, they make you think bigger is always cheaper but sometimes you're just paying for the giant package and the feeling of getting a deal.