Those costumes are fantastic and very realistic, even when viewed in close, as is often the case in the movie. That is not a costume. That's some hoax . . I don't doubt that the people who make sightings of Bigfoot, Nessie, Elvis, etc., are, for the most part, genuinely convinced they saw the real thing. However, if one understands the nature of perception, one should realize that what these viewers are absolutely certain of is a subjective construction built up out of the interpretation of their observations.
Many sightings are due to pareidolia .
Also, no one claims that every sighting is due to a hoax. Some are misinterpretations of visible perceptions, such as large animals or footprints enlarged due to snow melting, etc. Another thing that makes me laugh is the question about why there are never any Bigfoot bones or dead bodies found. The response to this is always the same, and that is to point out that there are never any bear corpses or bones found either, but we know they exist. I have seen grizzly bear scat, however.