I agree with most of what you said, including the highlighted point, but I wanted to add this perspective:
We all generally know how the casts of reality shows work. There are very few balanced emotions, with the focus being on bringing dramatic situations into the fold. On Storage Wars, you have everyone save for the professional flipper (Dave) getting lost in this notion that things are worth money and these things have immutable values. You see them trolling through the stacks of stuff placing $100 values on anything from coffee tables to guitars, as if they're already sold. They "win" each episode by accumulating these appraisals as if they've already been promised the sale of these items. I've watched about a dozen episodes and in every one, at least one person "loses" multiple hundreds to thousands of dollars. I'm assuming most of this money is their personal investment, yet they seem undeterred by spending boatloads of money on a general loss. The time they invest in going to these events, buying, moving, storing, and bargaining the sale of items is outrageous, yet they continue.
If like one poster said, people are flocking to these sales and throwing ever increasing amounts at the storage units, there's an even lower barrier to entry for thrifting. You could buy a whole rack of items, possibly containing a gem, for far less than a single storage unit would go for. I think the growth of thrift store shopping, even without media hype, has come to a point where I have trouble going through a store on the weekend. If the traffic DOUBLED, would there be any fun left in the hunt?
They will plant stuff. Otherwise, finds are too unpredictable and low to sustain a show.