First and foremost: I REALLY like this thing! The stream is intense! The massage is great on my back. As others have stated you will not know this is a low flow. It's adjustable from hard stream to softer to massage. I did not like the massage on my skull.
This thing retails for $10 on Amazon. But many folks (like myself) have gotten free ones through various outlets. Check your utility website for efficiency promotions.
I have seen ROI calculations like this thing will pay for itself in 5 months. Dunno, but I would definitely recommend it for the stream alone.
Niagara N2915CH Earth Massage 1.5 GPM Showerhead, Chrome