Ho replaced the traditional Nokia, Motorola and Japanese models with the newest iPhone and accessories. At its peak, some 80 per cent of what he sold were iPhone-related products and half his customers were from the mainland.
The thriving business, however, declined sharply in the past two years, especially after the implementation of the new Competition Ordinance, which seeks to prohibit unfair business practices such as price fixing and bid rigging.
Ho said big electronic chains such as Broadway were able to offer much lower retail prices, prompting smaller operators to follow suit. For example, the profit for a brand new iPhone decreased from about HK$300 to just HK$100.
"The business needs to be diversified," Ho said, adding the shop now also provides repair and data transfer services.
Another retailer, Sky Cheung, said he was thinking about quitting the business. He said the profit he made from iPhones was down from about HK$2,000 to a few dozen dollars.
"It doesn't make sense for me to keep on," he said.
The slump has also hit the real estate sector. A property agent at the plaza told the Post that about 15 percent of the shops on the second and third floors were empty, and the rest had had their rent cut by a third.
However, beside the factors unique to Hong Kong, the sale of iPhones seems to be losing momentum worldwide amid fiercer competition.
Apple reported its first decline in annual sales and profits in 15 years for the year ending last September, with iPhone sales down by 5 per cent in the fourth fiscal quarter.
"From a consumer point of view, the iPhone definitely transformed the smartphone market with its touch screen and user-friendly interface compared with the old [personal digital assistants] with a pen or devices with a button keyboard," CLSA senior analyst Mariana Kou noted.
Follow CNBC International on Twitter and Facebook.