I think people view for-pay information brokerage as unfair, unless it comes with service. If it's something they know costs the other party 0 marginal cost to provide, people start resenting them, which causes the paywalled service to hurt doubly hard when a free alternative comes about - even if they follow to free, people might stay away out of spite.
I think you are projecting your own personal views, or possibly views which are non-negligible in your social circle of tech-rich cash-poor twenty something males, onto the population at large. Empirically, people will pay for LOTS of things that have zero marginal cost. A short list: airplane tickets, gym memberships, list of bankruptcy sales in Chicago (my dad is a real estate agent and has had stacks of this weekly publication for as long as I can remember -- that info is expensive and worth every penny), and WoW.
I think I was probably off the mark in my post. It's likely not the marginal cost they're considering, it's likely just that $0 is the new reference cost for info in many people's minds.