What's your lifetime value -- 3 years is ~$360 -- so 1 more customer certainly justifies this price.
Also, I guess my suggestion is to have a more expensive option for those that are going to get a lot of value out of it. Even just segmenting 5/10 users vs. Enterprise would probably have us buying the enterprise version (I am part of a giant company)
Well that makes it a no-brainer. OTOH sending a note to my boss when our SaaS offering is $9/user/month would be a much harder sell.