On One Fatty on Bike to Work scheme is half price of the basic Pugsley/Mukluk offerings, but they aint twice as good, though the Floater tyres are pretty useless on dry sand i found.
You really don`t want a carbon bike for beachriding, wait till you bin it on greasy rocks- least the shredded bits will float 😆
Alloy will also corrode just as much as steel if untreated to salt water exposure, just look at stuff lying about on the coast to see that!,
Buy a cheap secondhand Pugsley then get a 29+ Rabbit hole wheel set, the Surly 29+ rims and tyres aint cheap but the rims have proved to be bombproof, get 2 bikes in one 😉