What makes Konbinis across Asia unique is that it's convenient, cheap and high quality. That's the magic sauce.
Most other places are super expensive or convenient or high quality. But hardly all combined. That's why Asian Konbinis are great. Note this is true of most of Asia, not just Japan.
Are they cheap, though? I often avoid going to shops the like of GS25, Żabka or 7/11, because the prices are often 125%-150% the normal supermarket price.