What Mors Kochanski famously said "The more you know the less you carry." could be applied here: "The more you know the less you pay." Knowledge about blade geometry, sharpening, steels, heat treats, materials, makers and so on, will make it unlikely that we buy something overpriced and end up selling it later, because it is actually lacking in some way.
The first step, of course, is knowing what we want (need) and this is where hype and pretty pictures are working against us, making us want what others want, or making us want what others want us to want.