Informal self-study training has the advantage that you don't need to invest in a training infrastructure. There are plenty of packaged solutions that you can buy off the shelf cheaply. These tend to cover the most popular areas of technology. The other drawback is that you may not be able to offer each customer precisely what it wants. Training is not support.
Dealers often fail to recognise the differences between the two.
They are sometimes under the impression that technical support can be a substitute for training. They can sell and support, but providing a coherent training programme needs a lot of other skills and experience. Second, you don't know what you don't know. Often a recurrent support call will come up because a person doesn't have good underlying understanding of a product. It's a symptom, not a cause of the problem.