Azure Video Indexer has moved under Applied AI Services. Create an Azure Video Indexer account does provide a little bit of documentation on the differences between preview, trial, and classic accounts:
When creating an Azure Video Indexer account, you can choose a free trial account (where you get a certain number of free indexing minutes) or a paid option (where you're not limited by the quota). With a free trial, Azure Video Indexer provides up to 600 minutes of free indexing to users and up to 2400 minutes of free indexing to users that subscribe to the Azure Video Indexer API on the developer portal. With the paid options, Azure Video Indexer offers two types of accounts: classic accounts(General Availability), and ARM-based accounts(Public Preview). Main difference between the two is account management platform. While classic accounts are built on the API Management, ARM-based accounts management is built on Azure, enables to apply access control to all services with role-based access control (Azure RBAC) natively.
If you've already seen this doc then I apologize and you would be right that this doesn't contain any pricing information. The move of this offering to under Applied AI Services is more than likely the reason for the broken link under service pricing. I've made the doc author aware of this issue so it can be addressed.