That choice existed under Obama. The law mandated that new construction would have low-flow water devices installed. You were, and are, perfectly free to rip all that out and install whatever else you want, if you're that stupid. Don't distort what the facts were to make a stupid political point. We already know you regard Obama as an uppity black man who never should have been President.
The $400 savings is an average, and is an actual figure comparing water consumption before and after the law, on a national scale. By a typical family, over the course of an entire year. It also includes savings from other low-flow devices, such as shower heads. Obsessing over the actual amount for a hypothetical family in Las Vegas is pointless. It might be $400. It might be $289. It might be fifteen cents (for a family that uses an outhouse and never showers, like many Republicans). What's the difference?
My point is valid regardless of the actual amount saved for any given family in any given location. Such devices save water. And if they're already there when you buy a house, you don't have to incur any out-of-pocket expenses to obtain them. So, overall water consumption is reduced. DUH!