I pay 3.34 EUR/per user per month. I use Gmail in my company domain - which is IMHO superior to outlook because of tags, which are more expressive than outlook folders. I use apps (some of them not available on Office365 at all - like forms/surveys, websites), calendar synced with mobile, google drive and group conference in hangouts with screen sharing (not working in Office365 in skype on linux - no good app for that)

Since use mostly linux - desktop version of Office365 is useless for me.

To sum it up: one third Office price - no functionality lose for me and some functions not available in Office at all.