Microsoft Office Macintosh Version: ~$79 after rebate

I am giving a few workshops at Montclair on PowerPoint, and I was discussing pricing on the Microsoft Office suite (Microsoft makes a student/teacher edition available at a lower cost). It turns out that Amazon is having a sale on it, for around $79 after rebate:

Microsoft Office for the Macintosh

The PC Version of it is ~$129 on Amazon:
Microsoft Office (PC Version)