Earlier quoted context omitted.
I do my best to find a local or online shop that actually knows & understands what they sell. Getting harder, but for more expensive items definitely achievable.
I have yet to find something on Amazon that I couldn't find at a local shop for within 5% of the Amazon price. I live in a very rural area, so I have to imagine that it's easier if you live near a city. Or maybe my sample size of 1 person isn't enough.
IE folks will take a 4 pack of something that sells for $20 and sell each bottle individually for $10 each.