Meaning, as a baseline, if I pay for a training I'm going to get more out of it because I'm psychologically motivated to do so because of the financial investment.
There are other ways to make someone "feel like they have skin in the game" but a price tag works.
The most recent online training I purchased was Brennan Dunn's "Double Your Freelancing Rate" course and it was definitely a good investment for me. It's easier to justify a course like this because it more of sales / marketing training and can quickly pay for itself in new business it helps you generate.
I used to subscribe to Avdi Grimm's Ruby Tapas which was another great investment at the time. I haven't purchased any of his courses, but Wes Bos looks to produce good premium content.