Given academic salary and researcher publication rate, I am confident that it is far less than $1000 you pulled out of air. How much did your tax go up when NIH mandated free publication, after a 2-years period?
Other open access journals are similar. Publication rates are high, because the vast majority of published research is NOT open access.
>But that financial model requires authors to pay a processing charge that can run anywhere from $1,500 to $3,000 per article so the publisher can recoup its costs.
They may have pulled it out of thin air (although I've seen similar numbers elsewhere, this doesn't seem to be in dispute).