APC - Article Processing Charge (i.e. the fee for publishing in Gold OA journals) is intended to cover the publisher's costs associated with publishing an article in an open journal (these are editorial costs - peer review, editorial processing, making available, archiving, infrastructure).

The fee is paid by the author's workplace or parent institution (department, faculty, MU), most often from project funds or support funds.

The fee amount is different for individual magazines/publishers, considering the different costs and prestige of the magazine. Various parameters and influences such as impact factor, selectivity of journals (percentage of assessed but rejected articles), competition and publisher's policy come into play.

The average price is around 2000 EUR (but the range can be extensive - from a few hundred EUR to more than 10,000 EUR). Specific amounts and other conditions (e.g. including the possibility to request a fee waiver, APC waiver requests - e.g. here) are listed on the magazine or concerned publisher's website.