Is 1688 Cheaper than AliExpress?
Yes. 1688 is meant to host direct manufacturers and wholesalers. So, the rates offered by factory owners would obviously be quite lower than the rates offered by distributors or middlemen.
At AliExpress, a wide majority of the sellers are 3rd party agents. These agents source products from manufacturers and list them on AliExpress by adding up their margins.
This, in turn, makes the prices of the product higher as compared to the prices offered by sites like 1688.