Formal, professional, semi-casual to informal... If someone says "I hope you are well", I will respond. The only thing that would vary, depending on formality/closeness would be the amount of detail I go into. Anything in 1-3 above would probably get "I am very well, thank you. I hope you are too." Personally, I would consider (it/myself) rude if I ignored it.

Informal would get the low down.
When I hear terms like "hipster" I think, who told cliques they could leave high school??