And they've managed to improve the latter while ignoring the former.

You get better prices, but the barrier to entry for buyers is substantially higher than Amazon.

There can also be a sales tax optimization game included. True for Canada anyway.

Then you have a hundred sellers selling near duplicates that may or may not be identical. Do you just buy the cheapest?

Do you buy it slightly cheaper in $AUD from Asia or in your local currency?

I’ve bought bike lights that used 2032s, then the same looking units a year later that had smaller heating aid cells.

Then there’s the lack of reviews, so you gotta détermine quality based on cues. maybe that vendor has sold a thousand units and Ebay links to some feedback for that exact listing.

Vastly differing return policies. And remember: when it comes from Asia and doesn’t work; just say it was lost. When Ebay asks you to return it, it’ll cost you more to ship it back than the whole item cost incl. shipping.

Just what is up with that account that has 3k listings but just 24 feedback?

But it’s definitely cheaper if you can manage all that.

A lot is product category dependent.

The lack of reviews doesn't bother me at all, as my experience is that reviews are worthless anyway.

So, I guess it entirely depends on how you're using eBay and what your goals are.

When I need it tomorrow: Amazon.

At least in Canada, there isn’t much in-between on the massive marketplaces.