We had several positions to fill, and we helped good candidates whom we couldn't hire get in touch with other employers. The chances of an interview were much higher than 1 in 15. In fact, we made eight interview offers.

The weekend was totally voluntary, not cheap for us, and everyone knew exactly what they were getting into. It was one weekend, not 15 weekends.

If you think weekends like that are inefficient, consider the job market as it operates currently. If you can think of a more efficient way for it to work, I would love to hear it.