I see a bigger (moving) picture. There is much to be gained by sending Pittsburgh talent to cut its teeth in LA. The benefits are more obvious if you consider study abroad programs. From The Chronicle of Higher Education:
Another important challenge in student mobility is that it benefits mostly only better-off students. For instance, most participants in study-abroad programs are students enrolled at four-year colleges. This is a point of concern if we consider that almost half of those enrolled in the nation’s higher-education systems are attending a community college. It is also disheartening that low-income and minority students remain highly underrepresented among those who study abroad.
Perhaps you don't think studying abroad has any value. If that's the case, then I'm not going to change your mind. But if you do, then you can appreciate how I understand brain drain and why I would promote the export of talent.
The people who least need geographic mobility benefit the most from it. International migration is a good indicator of an entrepreneurial disposition. This is the kind of talent that could create a job anywhere, including in her struggling hometown. Relocation, particularly to a dense global city, greatly enhances the economic benefits of a given skill. You'll do more in LA with your talent than you could ever do in Pittsburgh. That's not to say you wouldn't be successful in Southwestern Pennsylvania, tax credit or no tax credit. You'll be more successful in LA.
And you will be more successful if you speak another language and are intimately familiar with a foreign culture. Your prosperity is tied to your world view, which is tough to expand if you never the leave the confines of your parochial existence.