Hello, Mr. Marc,
We use the Kaltura Community Editon (self hosted, and free version) for our university.
Moodle plugins provided by the Kaltura Inc. can not be used with the Community Edition.
We have developed other moodle plugins as "YU Kaltura Media Package".
Therefore, no fee is required for software.
And, we are satisfied with the performance of the Community Edition.
However, the cost of hardware and labor is required.
Since update of Kaltura servers often cause troubles, it takes time to respond to the troubles.
So, operation experience of Kaltura system is required.
In addition, the Kaltura system will work with a single server, but multiple servers are required to obtain sufficient performance.
Because Kaltura server goes slow when uploading video or when periodic batch processing about database is running, you will need at least two servers (front end and back end).
As a reference, we use 7 virtual servers ( 2 front nodes, 1 load balancer, 1 database and data warehouse server, 2 batch servers, and 1 administration server).