Bob Campbell wrote on the Wiley blog:

"Stevan accuses me of much conflation yet he himself conflates APCs and subscriptions when commenting on double-dipping. APCs are not paying for the ‘same articles’ paid for by subscriptions. Publishers have always charged separately for different services/products. For example, a medical journal may charge a pharmaceutical company for reprints, advertising space and subscriptions. These are priced separately and charged separately, and accounted for separately in the publisher’s financial management of the title. The pharmaceutical company does not demand that the cost of buying advertising space is offset against any library subscriptions."

Bob Campbell defends double-dipping by citing journal charges for the purchase of reprints, advertising and subscriptions. That's all fine.

But what we are discussing here is the cost of publication, not of extra products or services.

Worldwide institutional subscriptions pay the cost of publication (in full, and fulsomely). It is not at all clear what extra product or service is being paid for when an author pays for hybrid Gold OA (for the paper he has given the publisher for free, to sell).

Of course it's an extra source of revenue to the hybrid Gold publisher to force the author to pay that extra money (for whatever it is that they are paying for). And let there be no doubt that the payment is indeed forced (if the hybrid Gold publisher embargoes Green). Is the extra "service," then, exemption from the publisher-imposed Green OA embargo?

(Note: If the publisher is among the 60% who endorse immediate Green OA, then none of my objections matter in the least, and I couldn't care less if the publisher earns the extra revenue from those authors who are silly enough to pay for hybrid Gold OA when they could have had the same, cost-free, by just providing Green OA.)

But the publisher who embargoes Green and then pockets the extra revenue derived from hybrid Gold, over and above subscriptions, without even reducing subscription charges proportionately, is indeed charging twice for publication, i.e., double-dipping (and offering absolutely nothing in return except freedom from the publisher's own Green OA embargo).

Subscriptions pay the cost of publication. Print reprints are an extra product. And adverts are an extra service. But hybrid OA is merely fool's gold, if paid unforced. And if forced by a publish embargo, there is a word to describe the practice, but I will not use it, as a publisher has already once threatened to sue me for libel if I do… So let's just call it double-dipping, with no extra product or service...