WordPress is designed to make it as simple to manage a website as it is to send an email. And it works. The continual updates and upgrades to the WordPress core continue daily through the community of WP developers and contributors who each contribute their own corrections and enhancements to be approved by the community for inclusion in future upgrades. This keeps the application growing and advancing to keep up pace with changing technology and needs.
The cost to upgrade? The same as the cost to purchase WordPress … ZERO. It is open source, a word highly offensive to companies especially like Apple and Microsoft. What is missing from WordPress that companies like that would provide if they owned the rights? Fees, snotty service and miscomprehended service manuals.