The Monthly Stock Saving Plan consists in buying the same stocks monthly, paying always the same amount (e.g. $1,000), rather than always the same number of shares (e.g. 1 lot). This way when the share prices are low you buy more, when it's high you pay less. Charges are low (hk$50, or 0.025%, whichever is highest).
Is it a wise investment, for those who don't want to follow the market?