AgentAuto.com is a privately owned site designed for a client and built on the WordPress platform. This site was designed initially with scale in mind. Despite WordPress being notoriously difficult to scale up highly, this site, at its peak, had over 130,000 listing pages for individual vehicles, as well as thousands of SEO-specific vehicle landing pages. Between efficient theme coding, caching, and a dedicated server this website is able to handle both a large amount of traffic and content very easily (never exceeding 3% server load, even when running cron updates).
This website is a good example of what WordPress is capable of given efficient coding and the right combination of hardware and software.