Good sailing foul weather gear has features you won't find on other normal foul weather gear. Things like retro-reflective tape, latex or neoprene seals at the wrists—which help keep you dry, and in some cases attachment points for safety
harnesses or PFDs.
Really good foul weather gear will last you years, and should really be looked at as a long-term investment. The cheaper stuff will not last as long or be as comfortable....you really do often get what you pay for.