Does it save the whole page or just the viewport? Just checked the landing page it looks targeted to a specific case of saving “screenshots” and this is also obvious from limitations in the pricing page so it would be unfeasible for larger projects?
It's primarily purpose is to render screenshots full-page or limited to viewport or an element. To do that well as it does the HTML has to be rendered perfectly first.
It's not as cheap as other solutions but we have customers who render millions of pages per month with us. They value the accuracy and reliability that's come from over a decade of refinements to the service.
Larger projects can request preferential pricing based on the specifics of the kinds of pages they are rendering.