@TS,
What you are asking is really hard. The reason why there are more Chinese products compared to alternatives is because of profit. For example your Bike helmet. The helmet as you say costs 1,800 php and made in China, If for example other brands like US costs 3k php. Now, supposedly when the retailer bought the china helmet for like 1.3k, while the US is at 2.8k or so. The retailer has more room to increase the price of the China made helmet rather than the US made helmet without it looking too expensive.
Thus local retailers usually stock the cheaper ones because they are the most profitable. And the cheaper the product the less weigh people decide on buying things.