How in the Nine Hells does any legal language entitle the company to charge him for something he did not buy?

Imagine buying something that costs over a thousand dollars and the company going “Oops we charged you twice well haha suck it.”

Binding arbitration doesn't mean you don't have recourse. It means the recourse is arbitration.

Winning might be out of the question.

"even if I don't get my $26 back, it will certainly cost them more than $26 just to respond so at least the cosmic accounting will balance out"