That depends greatly on how deep the domain knowledge at your company is, and the level of investment you make in your employees. If it takes 3 months for a new hire to even start being mostly productive (more than 50% productive and less than 50% drain on mentors' time) and 6+ months before they're really productive (90+/10-%), then the equation is very different. If you invest $10,000/year in employee training and development, you don't really want people leaving after 6-12 months, etc...

yes a company should provide a good atmosphere and have employees who want to stay, but if you're coming in the door with the plan to get paid for 6 months and then quit and try another startup.... then you'd be a net loss for me to hire