With only 500 subscribers, and I am sure you had more, that was a $1.5 million journal without page charges.
And, apparently, magically without expenses. The only thing left to pare from that budget was manuscript editorial, which, done properly, is more than moving commas around. And, of course, the publisher’s upper management itself, which ain’t going nowhere.
A quick glance at a recent Form 990 puts the society (fee-for-service) expenses at just over $800,000. For about 30,000 pages. Subscription revenue goes to the society. There aren’t many people getting rich here.