Amazon‘s a good source for household products that are compact and expensive vs their weight. (e.g. Toothbrushes, toothpaste, razor blades, etc.) My wife (who uses fancy shampoo) has gotten hers there, I use Suave and just buy from Target. They are usually not so good for stuff that’s cheap for the weight (large jugs of Tide) or bulky (toilet paper.) Cheap, heavy, bulky, stuff like Cat Litter? Absent a loss-leader or pricing mistake, forget it. It’ll cost a fortune for Amazon to deliver it, and they are going to pass those costs on to you.
That said, Prime Now (which I haven’t really looked into much) may be different, because when it comes to delivering to your doorstep, it’s the trip that costs Amazon a lot of dough, and bulk/weight isn’t as much of an issue, so their prices might be more reasonable for more goods.
Most of my bulk household goods (like toilet paper or paper towels) come from watching the Target and grocery store sale ads, and then stocking up when they have a good deal. (Occasionally my preferred grocery store will put the cat litter we use on BOGOF and I lug home 120lb of the stuff…)