The reason that none of the explanations make logical sense is because the theories presented only look at the demand side (Willingness to Pay) but the answer is on the supply side.
Theoretically the prices on concessions are already the lowest point possible for the theaters to still make a profit. In essence, all the demand side stuff the authors mention is correct, but they mistook what the actual marginal cost was.
The movie theater business is a surprisingly low profit business. Net income accounts for less than 3% of revenue (http://www.google.com/finance?q=NYSE:RGC&fstype=ii)
Theoretically the prices on concessions are already the lowest point possible for the theaters to still make a profit. In essence, all the demand side stuff the authors mention is correct, but they mistook what the actual marginal cost was.