I'm only partly sold by this argument. True, 'free' training is never always free - there's always a catch even if it is the car parking ticket. I made a conscious decision not to run free training events as a view to buy-in customers as anyone who wants an expert-level course already knows what they are planning to buy.
When its the case that your customer knows what they want the question is more around your credibility against their normal supplier. As we strongly promote the quality of our courses as set by the fact that we use official courseware, expert trainers (with experience and who have passed the relevant exams, also are registered to deliver the material), our quality rate is high. For excellent service you expect to pay for an excellent product, however as our team are small we have lower overheads and can do some things such as on-site training which are competitors are not in a position to offer.
So perhaps the argument should be more about why you should buy training that it not free. Rather than keep up with the latest new trends we as IT professionals should focus on getting our exams done and remaining compliant. After all, knowing how to do something properly keep us in a job.