As online shopping sites buys goods directly from manufacturing companies, and their orders are much bigger than local shops, there is no middle-man between them. so, they get huge discounts from manufacturer and hence they can give discounts to their customers also.
for example, A local shop ABC demands product X to distributor (say 100 units) and then distributor forwards this request to company. That distributor will hike price of that product and sells it to shop ABC. So Local shops are unable to give big discount
Where if a Big online shopping giant can directly contact companies and buy goods. so they get products at lower cost and they can sell it on low cost.
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