Where the Manfrotto product would keep the leg from sinking in, that also is a potential problem because it offers no lateral stability. The tips of the legs in the sand would solve that problem, but the legs could sink in farther after you've got set up already, big bummer. It's happened to me a bunch.

Thrift stores seem to have ski poles fairly often. I knew a guy once who actually did snowshoe with his 4x5 and he would affix the webbed feet from ski poles just a bit above the end of the leg, so the tripod would both sink into the snow some and also ride on top of it. I suspect that would work at the beach as well.