How to reduce the customer acquisition cost of e-commerce?

The customer acquisition methods in e-commerce, besides conventional approaches like SEO, SEM, EDM, TikTok, Facebook, and Instagram, do you know any low-cost customer acquisition strategies? In order to reduce customer acquisition costs, you have tried multiple sets of advertising materials, content materials, and multiple rounds of A/B testing strategies, which incurred significant costs in terms of manpower and time. However, how much has the customer acquisition cost actually decreased? E-commerce merchants have been racking their brains and depleting their wallets in pursuit of large-scale customer acquisition while the results are not significant.