AliExpress doesn't provide free shipping, seller does.
They buy one time package rather than paying money every time you have send something. They tie up with Government courier service such as China Air Mail and buy their package. This is similar to buying in bulk if you buy a single product it will cost for example 5 dollars but if you buy same product's 100 pieces it will cost you half the price. Similarly, buying package from courier agency turn out to be very profitable if you send item daily. Some seller then adds it to the product's total value(not in shipping charges)
A normal individual can buy a package from courier service provider in their area. It could be government or it could be private.
How can aliexpress offer free shipping?
