Wow
That sounds great and yes it's about 2/3rds of the cost taking into account consultancy fees as well.
You shouldn't just be concentrating on the SMB market either, check out the education sector, they would love that sort of intranet technology especially at 2/3rds the cost of a MS Sharepoint Server install and setup.
Shame this wasn't around awhile back the FE college I currently work for would have liked the cost savings (more to the point I would have liked the cost savings, my budget was stone dead after implementing the full cost MS version, no new toys for me this financial year, roll on August).