Mr. Ernst says the mine shaft is 30 feet deep. But later, he, Ted, and Buddy stand on each other's shoulders to allow Buddy to escape. Buddy's outstretched hands would only be about 15 feet above the bottom of the mine shaft, which is still 15 feet below the top. The top looked like the bottom, so climbing out at that height wouldn't be any easier than climbing out from the bottom, which they couldn't do.