i went and bought the hired mercenary today and realized that my upkeep nearly doubled to 5B when i installed it. the upkeep says 2.5B at level 1. i went through and checked all my other items upkeeps and none of them come close to 1B my highest upkeep item is just over 500M, and that's my heavy artillery. Is this a typo on the upkeep of the item because that adds up to a whole lot after all leveling is done?

I kind of noticed the same thing - I'd install items and my upkeep would go up and even after selling them it remains the same?

No, that is the correct upkeep.