>Training for a niche industry may be much more expensive because I can’t afford to have a standardized training program, and some employees have to be unproductive to teach the new employee how to be productive.

I vehemently disagree with this. If your training is so niche as to not be standardized (and thus, have value in the marketplace), you absolutely should not get to go after the employee. If they leave? Tough. Work on retainment if you wish your company to be successful.

With this line of reasoning, every business down to restaurants with fry cooks could argue they are imparting valuable wisdom and thus hold their employees indentured. This is not some hypothetical to me. My ancestors were indentured servants to the Jamestown colony.