This may sound lame, but another factor to keep in mind is, "Paying more for quality."
One oft-repeated story is the deli-counter with two jars of pickles, one for $1.10 and one for 85 cents. Same exact pickles, mind you, but some people like to pay a bit more for quality. If your belief structure is such that you believe you can't learn something as life-changing as PhotoReading for under $20, then you may need the seminar or the tapes.
I think this is one of the reasons that I purchased the tapes.
Other good thing about the tapes is that it's an auditory reference to a visual art. While one cannot PhotoRead with "PhotoReading" at hand, one can do so with Paul Scheele guiding the process through one's ears. I believe that this, combined with the task-master "it will work, this is how it works, do it, you'll see that it works" re-assurance, makes the tapes worth the extra price involved.