Apple shares have been trading at sky-high values, hitting a record $600 recently, though an odd glitch caused a halt in trading Friday morning. A single trade of 100 shares at a price of $542.80 from the BATS Exchange caused a momentary plunge in the value of Apple shares. Trading was halted, due to the so-called circuit-breaker rule that is invoked when great volatility hits a stock. The trade was apparently a glitch and Apple shares recovered to $597.25 by early afternoon trading.