The rhetoric of access in academic publishing is full of metaphors (open, toll, barrier), including the notion of "access" itself, which is actually a metaphor for acquisition. "Open access" is stated less metaphorically as "free acquisition." After all, acquisition of content is not the same as content access. Literacy (three kinds here -- functional, domain-specific, and contextual -- that is, a physician from 1920 would be lost in a specialist medical journal article today) is a key component of access. An engineer acquiring a geology paper may find the content quite inaccessible on an intellectual level. "Access" is a metaphor for "acquisition" in this case, and not a metaphor for "comprehension" or "understanding." Yet often the metaphor of "access" is loosened to feel inclusive of comprehension or understanding, as this serves rhetorical purposes. For instance, "public access" is used as a metaphor for making research content free for non-specialists to acquire.

One metaphor that has persisted for years is that of the "pay wall," normally written as "paywall" but separated here for clarity. The "pay wall" is a metaphor worth contemplating, as exaggeration of the impassibility of payment systems via this metaphor has led to all sorts of strange behaviors, accusations, and social complaints.

The "pay wall" metaphor is almost unique to online content purveyance and normal commercial transactions. There are many other transaction points put in front of acquiring something which we don't refer to as a "pay wall":

a toll booth on a state road
a parking meter
a cover charge at a bar
a ticket to a movie
a shopping cart in an online store
a service charge for a concert ticket
a subscription requirement for Netflix or other streaming services
a postage stamp

None of these is considered a "pay wall." Examples of payment points after you seem to have acquired what you came for -- a checkout line at a supermarket, a bill at a restaurant -- aren't considered pay walls, either. In fact, like the others, avoiding these is usually viewed dimly, and some carry fines or threat of arrest.

Why these are considered normal transactions in a demand-driven economy with fiat currency and not "pay walls" remains elusive. The purveyor has taken the risk of putting together something of potential value, and then asks others to pay for the privilege of using these materials, services, or spaces. There was a decade during which the mantra "information wants to be free" was prevalent, and only some correction to embrace the entire quote drove this from the field of play.

Yet, when it comes to online content -- mostly newspapers, magazines, and academic journals -- we see the metaphor of a "wall" used to describe the transaction request. The metaphor is extended to include a "gate" at some point, and sometimes a "meter" if the gate adds counting as part of how it solves the "gating" activity within the "wall." But the "wall" aspect is so ingrained that even metered transaction systems are referred to as "soft pay walls." I imagine an inflatable wall, which makes for a very poor metaphor.

As others have pointed out, Gold OA itself does not do away with the notion of a transaction barrier, but merely moves this transaction barrier to the author and to the point of acceptance, rather than to the reader and at the point of content acquisition. Nevertheless, this transaction point is not itself referred to as a "wall" of any sort. It is given the more technocratic and obscure label of "APC." There is no metaphor at all, so the term is neutered rhetorically. It can't inflame anger or a sense of injustice as it is currently positioned.

The metaphor also fails often since most online content in newspapers, magazines, and journals is acquired through licenses or subscriptions. The "pay wall" is usually invoked when someone encounters content for which they or their employer have not established a license or subscription.

Metaphors work well when they inform, poorly when they mislead. The best metaphors allow you to anticipate how things might work based on what you know about the associations created by the metaphor. For example, calling someone "boiling mad" is a way to let others know that there is a simmering rage that might spill over if the person is pushed. You can anticipate, and plan accordingly. The same for "wooden faced," which lets you anticipate that someone is perhaps hiding their true feelings, and may require more consideration or care during interactions, as they don't show their reactions easily.

Calling transaction points for content "pay walls" isn't a helpful metaphor, as it suggests only a few alternatives -- bashing through the transaction point, scaling over the transaction point, or turning away from the transaction point. It suggests there is actually no clear passage through the transaction point, which may be why the metaphor has gained popularity among those who feel it is illicit for content companies to ask for payments. In academic publishing, this has been a particularly fraught area, as the notions of taxpayer-funding and moral rights make the metaphor of a "pay wall" inherently inflammatory to some.

Of course, a subscription or license remains a viable and often inexpensive alternative, but the emotional payoff of using the "pay wall" metaphor remains tempting to those seeking to make a point.

Publishers have not done an especially elegant job of constructing their transaction points. One mistake has been to put the per-article (or pay-per-view) charge front-and-center in many cases, rather than cheaper and attractively packaged subscription options. These clumsy transaction points come off as tone-deaf at best, arrogant at worst, and certainly can provoke a negative emotional response. It's like there's a simple turnstile with a person standing in your way, scowling and arms folded. The path should be clearer.

New approaches to content transaction points hold some promise. Metered paywalls (again, the metaphor persists) have many more elegant options than traditional binary transaction points, including softer messaging as the meter increments, better interaction models, and more sophisticated modals and interstitials that can be contextual and smart.

This may be the path forward -- breaking down the "pay wall" into a "pay path." There is plenty of evidence that if you provide people with a reasonable and pleasant way to pay for what they want, it works. The challenge for academic publishers is to adopt these practices quickly enough so that the metaphor changes sooner rather than later. We don't have time for more walls to be built.