This argument gets rehashed every 30 minutes or so in some forum. The "stuff freely available to download" is most likely pirated, already. By law, pretty much everything we do in the "retro" communities at this point in time is copyright violation, and there is no legal concept of "abandonware." With notable exceptions, we generally fly under the radar and even when caught sometimes we get thrown a bone. For instance, ask yourself why Nintendo, knowing the Commodore 64 port of Super Mario Bros. was in development, waited until it was completed and released to drop the hammer.
In my experience, eBay does not have a very good track record of taking down auctions like this when reported by users. Exceptions are for eBay's own trusted users, generally ones who are active in forums and have a history of involvement with legitimate take-downs. Users who actually own copyrights for an item (software, literature, etc.) which has been copied without authorization will also have better results. Even so, as is well documented at AtariAge and other forums, real scammers are a cancer and just when you think it is gone it pops up elsewhere. In the case of eBay cancer they will hold multiple accounts simultaneously or simply create new accounts to peddle their wares, both of which I believe are violations of eBay policies.
But the question raised is: what exactly is a scammer, and is something like this a scam in a strictly legal sense? Are shareware collections on optical or magnetic media scams because the contents are shareware or otherwise freely available? If not, does providing the collection as a digital download make it a scam? Does the person or persons bringing scattered parts together not deserve some compensation for the time involved? Given the scenario of a potential buyer who is not savvy or does not want to ask Google where to find issues of "99er Magazine," does the individual satisfying the want not earn some desired compensation? The majority of the work I do is based upon my intuition, knowledge, and experiences, but more of the day-to-day stuff is research-driven -- research which any user could do themselves but are willing to pay me to do it. Have I scammed them?
Even in the sense of research (read that as, Google,) or the Wayback Machine: these are not free resources. Anyone who uses Google provides something of value in exchange, and the Wayback Machine is supported by monetary contributions. Ethical and moral arguments notwithstanding, from a strictly legal perspective have they scammed anyone?
Then comes the time when I have to, again, rely upon my own experiences. While I may feel amoral for doing so, if someone insists on paying me for a collection of something which they could put together themselves, what if their morals hold so such objection? While some may feel it is unethical for me to withhold knowledge which I have built over years of my own work, my ethics hold this information as valuable and deserving of compensation. I could change the oil in my car but I choose to pay someone to do so, and they are ready to accept my money.
So long as the person selling a collection of PDFs does not present the sale such that the buyer expects a box full of magazines, and the publisher of the magazine, which I am absolutely certain has its brands and trademarks monitored, has no objections, then the problem is nothing more than the subjective observation of an outsider. The same applies to producers of any good. A healthy free market regulates itself by way of producers, sellers, consumers, etc., and, as no system is perfect, will always contain an area of illness.
Given I am an outside observer and I hold no authority over a transaction, I am in some cases inclined to report to eBay. I understand eBay maintains a list of brands which have filed complaints and can quickly identify if a particular item would fall afoul. But as I also like to make sure I am part of the signal versus the noise, I could thus be inclined to do my own research to determine if a particular brand is still owned and protected, then contact the rights holders.
Then, is the guy really making money off these sales after eBay and PayPal fees and time involved in gathering, listing, and responding to sellers? Who pays the hosting if he is not using something like DropBox or OneDrive to host the files? How do we know how much time and effort were expended on his part, and who, if not the buyer, has any legitimate claim on a value for that time? If all legal questions and obligations are satisfied, which also makes the comparison of stealing from a car non sequitur, and he is making a buck off the deal, who in a free market has the to say how much money he should make and for how long?
tl;dr If it satisfies your morals and ethics, report the buyer to eBay or contact the rights holders, but do not be disillusioned if the auction remains in place nor that people are buying. If the people buying are being scammed this will be a lesson to them. Until proven otherwise, we are not part of the transaction and are operating upon personal prejudices, and whether or not the guy is stealing depends upon assumptions. Everyone who sells puts a value upon their own work, irrespective of the end product and its source materials, as does everyone who buys.