Here's an example of a well-made holster:
And an example of the other end of the spectrum:
Being on travel, I'll have to add the explanation of each keyline later.
One does not have to spend more to get a well-made holster; what's required is (1) that a maker knows what's needed, and (2) that you know how to recognise the key indicators that he/she's got it right.
This post is strictly about key indicators of construction, not design or materials or ergonomics or features; which perhaps I'll cover in future posts.