TYPO3 is a CMS with its own content model, extensions, permissions, and publishing workflow. A migration estimate based only on page count will be wrong.
Inventory content types, languages, assets, redirects, forms, user roles, scheduled publishing, and custom extensions. Copy a representative section to a test instance of the candidate. Ask an editor to update a page and publish it, then check rendering, accessibility, SEO metadata, search, and rollback. Verify old URLs and redirects; broken inbound links are a migration cost too.
If the reason for switching is maintenance, compare the ongoing work of upgrades and extension compatibility, not only the first build. Keep the current site and a content freeze plan until the new system has passed an editorial and technical acceptance test.
Akousa