Back when I knew about such things, eBay had a policy against any one
seller having more than ten identical items listed at the same time.
You could complain and eBay would close the extras, at least, and
sometimes all of them. I bet that doesn't happen much these days.

I agree that the joy of hunter-gathering on eBay is nearly gone. When
sellers didn't know what they had, and buyers eagerly relieved them of
the responsibility to find out, it was surely more fun. Actually it
isn't that much different today, except everyone knows the value of
everything, if they take the trouble to learn and use their tools and
knowledge. But it isn't as much fun as often.

And have you actually complained to eBay about multiple listing sellers?
(many are drop shippers...not crooks  anyway).

Or did you think you'd just whine your a.s off here to a community who are
made up of many individuals some or many of whom have the intelligence and
sense to be able to use the filters on eBay to sift most of what you
perceive to be a problem outta the way in the first place?

As an aside I used to go to local general auctions to buy trinkets and stuff
to sell on eBay (and Yahoo auctions before eBay acquired that). But I
stopped when lots of other people without a clue and too much money started
turning up and bidding up the prices, in many cases way over full retail
price, for stuff at them. Isn't popularity a bitch?

It is imo only a matter of time before manufacturers of globally available
products will either cease to supply bricks and mortar stores or to devise a
pricing structure whereby it doesn't matter where in the world you buy x
product the cost is the same.

In the meantime consumer is still king and if you have the ability, sense
and funds to research your purchase probably bargains are still to be had.
Whether by taking advantage of exchange rates or hard negotiating skills in
a bricks and mortar store in your home country.