They cost as much or more than a conventional aircraft and they couldn't fly over weather. Landing and getting the payload on shore was also a problem. Nobody ever got a formula and mission for the concept that made sense.
Now, if you wanted a fun toy and the FAA considered a little one a boat, you might have something, but the market is small.
Geoff
Who thinks just looking cool to eight year-olds, is not a justification for production.