A lot of things are actually LESS expensive in stores. All that speedy delivery adds a lot to costs that are baked in. Sometimes things on Amazon are 50+% more. You have to know your prices to know what’s a good deal vs what’s a total ripoff.
IE folks will take a 4 pack of something that sells for $20 and sell each bottle individually for $10 each.
My rule of thumb is that every not-heavy product has about $7 of shipping costs baked in somewhere. For cheap items, there isn't enough markup to cover those costs, so they are usually higher priced than at retail. If it's $50 or more, there usually is, and the amazon price will be competitive or better than retail.
For heavy things the shipping ding is bigger, but they also usually cost at least $30. No one bothers to sell $5 items like 50lb bags of basic sand on amazon.