I love custom made clothes in theory because I have my own very specific ideas of what I want.
Reality, though, is not that easy.
No matter how well you communicate your ideas to the tailor and how skilled the tailor is, dressmaking is an art not just a skill...even if it fits your body perfectly, 2millimeters extra here and there as well as tiny variables such as thread hue and lining texture could make or break the entire outfit and you could end up not wearing it. Many friends, even those with much experience with tailors, have had similar experiences. Now I only ask dressmakers I can bug day and night about these details and go to numerous fittings (i.e. friends&relatives!), or whose impeccable taste I trust completely (if I can find anyone). Just be aware that a very real risk is there, often at a high price too.
In that sense, you know exactly what you're getting with store-bought items.