Unfortunately, there is no way to expand the limit on the number of pages for one project in Tilda (500 pages max).
You can bypass the 500 page limit through the Business plan and subdomains. With Tilda Business plan, you can create up to 5 projects within one account (500 pages each, 2500 pages in total). For example, you assign "yoursite.com" domain to the first project, "news.yoursite.com" – to the second one, "blog.yoursite.com" – to the third one, etc. Link the projects.
You can also export Tilda made pages to your server and thus bypass the limitation.