The price of forever ranges from a few hundred to millions depending on how resilient you want to be.

In reality, it would probably be more effective to dedicate nearly $0 to infrastructure and $N,000.00 to an endowment for 1-3 hours of engineering time each year.

Figuring out how to host a static site for free and moving the site to that service requires almost no time for a competent engineer. But finding a solution that is guaranteed to exist in 100 years with zero human intervention would probably cost millions...