100% untrue.

Let's say I have 50 employees working for $100,000 each.

Why would I not want to replace 25 of them that are willing to work for $50,000 each if they are producing anywhere close to the same quality.

In a case like this always open job listings are a warning to others.

Also there is something called market sampling. Where you put up these job openings and look at the quality of applicants in relation to the employees you already have to ensure you're on the right track internally.