The original Dopie was designed by Matthew Harrison while studying at the Royal College of Art in London, England. He created the Dopie knowing people would be thrown by their lack of straps, but he remains confident that because of the toe-hold, straps are an unnecessary evil.
Prices can vary wildly, so it pays to search around.
A few reviews of the sandal are online: one short term use; one long. The latter also links to info on why the Dopie Sandal is also v. good for your feet from a biomechanical point of view.