There have been quite a few 'scam' offers like this going around the Internet over the last few decades. Basically they bulk email known academics offering to 'publish' their work for a fee on what sounds like a real academic site. The basic scam is for them just take the money & run. When the victim then looks further they find the site never was a real academic site or even in any way connected to a school, college or university, usually there is a single letter changed in a name. Others will actually put the article on line somewhere, often with fraudulent claims of peer review (the 'peers' have never heard of them) and no editing, and/or with malware embedded in either the site or download package. And they then have a real contract that gives them exclusive rights to the article so the author can't publish it on any legitimate site without paying an extortionate fee to the scammers to buy back their own work.
Yes, there's been a good amount of scammy offers around. In this case, though, I'm not sure it's a scam, though I don't know the journal and I did not take the time to look into it any further.
There's quite a few journals that post lots of things open access without a fee, but academic publishing has always been a somewhat special beast. I know of people who paid quite a lot to have their thesis published because the publisher had "a good name" and it was prestigious to be in print there. The thesis itself was not cheap to buy once it was on the market, too - and as far as I know, the authors never saw any of the book's profits. Things like that make me a little sad...