You can't beat that price. I paid just under three times as much for my copy. This company is legitimate. I received my first order from them last week.
Great thread on Silver Bayonet on this forum:
https://wargamesatlantic.com/community/xenforum/topic/78263/the-silver-bayonet-projects
Brief discussion on Silver Bayonet during the French and Indian Wars:
https://wargamesatlantic.com/community/xenforum/topic/78358/french-and-indian-war