In theory...in theory. But not in reality. The reality is this:
(1) The "prevailing wage" is defined in bands for general positions. This means they can pay 100% of the H1-B's the absolute bottom wage for the the band.
(2) They can "define down" the title of the position to use a lower wage band. And they do.
(3) There is no checking up on them. Basically, they can declare a position to be whatever title they want. No one comes and tells them -- you wrongly allocated this title. Therefore, there is no sanction on this behavior.
(4) Many, if not most, H1-B's work as contractors. Thus the company that hires them doesn't hire "them", they have a contract with a contracting firm. Therefore, none of the above (1) to (3) apply, because contracts are not subject to the same criteria as employees. I can create a contract opportunity tomorrow, contract someone for 3 months at 1/3 the wage of what I would pay an employee, and keep extending the contract. Since the person filling the position is not an employee, I can pay what I want. If there is a violation of the law...well, heck, it isn't ME that is violating it, it is the contracting firm. Which, by the way, is often a small 10 - 20 person body shop which flies under the radar, or a foreign owned firm anyway.
So...the theory and the reality do not correlate. I speak from real world, practical experience on this.