My understanding is that Udemy gave them very little control over the pricing of their courses. They would constantly have highly reduced prices on the courses and then run specials, although can you really call them specials when they are run constantly, on courses and sell them for a 90% or higher reduction.
For anyone that has written online training that can be very discouraging as it takes about 8 to 10 hours to write 1 hour of training. When you price your training you try to keep it competitive and still make profitable. As this is a very competitive market you have to price it accordingly. Then you see your classes being sold at a 90% or higher reduction, there is little to no profit in that model for the instructor. Of course Udemy likes it as it moves much more product, and they are in to quantity and not quality.
This significantly cut into the money they would draw on the sale of the courses, as most times the percentages would not change with the reductions in the price. There was a delay in the length of time it would take for an actual sale to be reflected in the accounts of the instructor, as Udemy would hold all sales for the 30 days that the guarantee was in effect and then wait for the following months payment window. If the sale was timed correctly this could result in a delay of almost 90 days from the time the course was sold until they actually received payment.
You can opt out of their cost reduction but many of the benefits of the Udemy marketing model are not available to you if you do.
I considered putting some of my courses on Udemy but after reading through their contract and speaking with the instructors that I know personally that have listed their training there I thought better of it. The payment schedule, the price control and the fact that you sacrifice the ownership of your training materials once it is on their site, there is no way I would do that. I could not effectively support my students if I were to do that.
On closing I will say, I have followed what they are doing for the last few years and they have seen a significant drop in their sales and site traffic. I think it has more to do with the quality and support of the training then anything else. It is difficult to get instructors to support their training and keep it up to date, when in my opinion, and many of the instructors opinions, they are being taken advantage of.
I think the affliate program is interesting. From what I have seen, this program and the pricing model will once again cut into the percentages that the instructors receive. Which in turn will start that circle again. Paying them even less for their work. I think Udemy has yet to realize that the quality of the content of the training, the quality of the instructors and the support those instructors give is what will make the site effective and profitable. They seem to be putting in place business models that undercut that effectiveness. In my opinion, eventually they will lose all of their good instructors.
Again strictly my opinion based on what I have seen, the instructors I know, and the support I have received.