For example, you could argue that Google Analytics is a Freemium version of Google Urchin. That costs $9995: http://www.google.com/urchin/pricing.html

(Of course, Google has a different business model for Analytics - basically they want to commoditfy the complements to their advertising business. But my point here is that freemium can work well in enterprise software with less than 100K active users if the pricing is correct)