Costs of EDA Tools
The Mentor P&R tools are not as popular as SOC or even Astro. And I can understand that because right now SOC, Astro and Olympus are technically better than the current Mentor solution: Faster, more supported, more features, etc. That is why they don't charge as much for IC Station. Plus there are areas where SOC and IC Station don't overlap, like IC Station does schematic based design and Layout. Also, SOC and Astro can handle larger designs than IC Station.
But after this news of the merger/buyout with Sierra-DA, the Place and Route market will change. Mentor will probably integrate Olympus with their flow and start charging a lot more for their tool.