I have subscribed to the Pro plan, which states that there are unlimited views. However, will there be additional charges for a large audience? If so, at what audience size will extra charges apply, and how much would those charges be?
All 8th Wall plans and commercial licenses include unlimited views. There are a few rare rare exceptions and you can find all of the details at
8th Wall | Pricing and Plans - WebAR, AR, WebVR Developer Tools and SDK - refer to “What are the restrictions on unlimited views?” section.
Would you mind sharing details on the project in question and the amount / duration of traffic you are expecting?