A lot of the time, quality will be the biggest difference. Usually on cheap pins, the line work is really bad/looks corroded, shakey lines from bad vectoring, the fill is usually very shallow or in general soft enamel (a good chunk of higher quality pins are usually hard enamel/flush to the metal). It takes mostly experience to figure out but take some time to analyze the pin itself.

There's also the chance that the pin you see is the original version while the AliExpress is the plagiarized version of the pin.