Finally, I tried 大生腸,腎,豬心 today, because it was only 3 or 4 customers waiting.

HK$5 for 腎 and 豬心, which is cheaper than most of the store now. And HK$10 for 大生腸 but bigger serving than other stores which selling the same item for HK$6.

Taste is only as average, nothing special. But the store is not that mess and only single item, so I believe that the price and the store is the reason for people to fall into the line to buy from them.