Amazon has taught me to go out of my way to buy directly from manufacturer or a reputable retailer that doesn't offer third party sellers on their website.
I don't want to save 10%, 20%, even 50% to risk any chance of getting some counterfeit crap. Hopefully, there will be sufficient customers like me to make it economical to offer quality, vetted goods at whatever price it takes. Sadly, I see even target.com now allows third party sellers.
I wouldn't care about third party sellers if the retailer explicitly mentioned they don't commingle and allowed me to restrict all of my searches to items procured, shipped, and sold directly by the retailer.