that's a very good question, even though the labour is contributed, the cost of building materials and these high end video production items will come to a very serious amount of money. (also some specialist works beyond the scope of volunteers may have required contractors and the're operating a business so of course will have been paid out of donated funds)
Although the final videos are provided freely without charge, they aim to make a version that is the most accurate ever made.
The first episode is a taste of things to come. You just know that the film set is going to be in use for some years as the first episode is 1 hr 11 mins and Jesus is only 12 years old and really hasn't done anything yet 🙂
and I don't think they can manage more than 2 episodes per year.