Technically if you have more people competing for a smaller pool of jobs, then H1B shouldn't come into it.
If you're talking about H1B's competing for the job...well the salary should already be set at 'market rates' per the H1B process.
So...US jobs don't get priced lower as a result. Since the job is so critical and they can't find candidates it typically would be at the high end of the cap. They would even pay MORE because the position is for a highly sought engineer.
Oh...right. Sarcasm. This is why H1B needs to just die a fiery death.