If you need more than four nodes, the price is more than flexible. Also, we always try to understand better customer infrastructure and, case by case, give node free of charge at all—to cover all the customer's network perimeter. Don't want them to sacrifice part of the infrastructure because of stupid license/price limitations.
In fact, Wallarm Node is much less black-box than most of the commercial security products (with their own operation system you don't have access to, updates no one knows what inside is, etc.). It is predictable in configuration (just new directives in nginx.conf). Scripts, which come with the Wallarm Node, are free to review. In-memory storage (used for fast local analytics) is accessible. You can watch what the data is exchanged between Wallarm Nodes and Wallarm Cloud. And you use operation system you know.
With our customers, it's OK for us to share source codes.