Sure, I can see that. String them along--just as long as they aren't "the guy." (You know, the only guy that understands how the mission-critical systems work. I've seen companies go under when they lose that guy, without a knowledge transfer, which may take months). The replacement coder costs the new going rate, delivering a fraction of the productivity in the months before they have equivalent institutional knowledge and understand the wage refugee's code.
Ironically, even if a penny pinching manager did save a little, it's behaviors like this that drive IT wage inflation.