They have different purposes within a website. A page normally keeps its position as one of the main topics. For instance, Home, About, Services, Blog, and Contact. Pages don't change position much. A post is content added from time to time, usually anchored by the Blog gateway page. Posts can have a different layout from a normal page. Sidebars are common, especially to display the most recent posts. Also, a post archive can be offered, plus a search option and a contact button. But for SEO pricing purposes, page = post.