It's better to think in terms of risks not just costs. Interviewers tend to higher people just like them, which means the team is often filled with people that think the same way and come up with the same types of solutions. On the other hand when you get someone in that can 'do the job' but has a radically different perspective they are more likely to bring something new to the table. To be overly simplistic in a team of world class programmers adding someone with a great UI background can be worth a lot more than yet another world class developer. The advantage being diversity does not require a larger paycheck.
It's better to think in terms of risks not just costs. Interviewers tend to higher people just like them, which means the team is often filled with people that think the same way and come up with the same types of solutions. On the other hand when you get someone in that can 'do the job' but has a radically different perspective they are more likely to bring something new to the table. To be overly simplistic in a team of world class programmers adding someone with a great UI background can be worth a lot more than yet another world class developer. The advantage being diversity does not require a larger paycheck.