Stick with official stores from reputable brands. Don't order shit from sellers like GoldenRandomBrand24723. Don't buy shit from shady stores with 10 reviews. Don't buy shit from stores whose pricing model is based on charging high shipping fees and low prices. Don't buy shit you can't return.
Basically, don't do deals where you know upfront the odds you'll be screwed without any recourse is high.
Online stores sell products, but you need to get your head sorted out and do the thinking.
The fact that the answer is "look through all the reviews to see if they're shady, check the seller, check the sellers reviews" is an absolute product failure by Amazon. I shouldn't have to do scam research to buy a toothbrush.
You make me suspect I might be using Amazon wrong. Amazon's search is notoriously bad, but if you know what you want them you can go there and buy it. Just don't do stupid things like buying a 20 dollar item whose cost is 1 dollar price with a 19 dollar shipping fee, or buying weird things from shady sellers who just dropped by out of nowhere.
But that's just me. Perhaps I'm using it wrong. Who knows.
"Genuine Original Oral-B Braun Precision Clean Replacement Rechargeable Toothbrush Heads..."
$31 for a ten pack. Seems probably about right? But when I click through the full title is:
"Genuine Original Oral-B Braun Precision Clean Replacement Rechargeable Toothbrush Heads (10 Count) - International Version, German Packaging"
and it's sold by "Wiki Deals". The photos show a package with English labelling, for what it's worth. So I guess these have been imported somehow? Are they legit? What does that mean for FDA approval, I wonder? I don't want to have to consider these things.
By contrast when I search Target, the first result (including any promoted stuff):
Oral-B Sensitive Gum Care Electric Toothbrush Replacement Brush Head
It's a three pack, $21, sold by Target themselves. More and more I'm just going to Target in the first instance and skipping Amazon entirely.