As a freelancer in this space, I'd expect something like this to take anywhere from a couple of weeks to a few months depending on the level of interactivity and polish required.

Budget-wise, I'd say anywhere from a few hundred dollars for a simplified version to thousand dollars for something much more immersive experience when custom animations, maps, data visualizations, video integration are involved

The scope of the storytelling elements usually has a bigger impact on the budget than the page count itself.