sometimes I order stuff from china and I get it in less than 1 week even if it feels like I don't even pay for shipping, why don't they make more warehouses ove

sometimes I order stuff from china and I get it in less than 1 week even if it feels like I don't even pay for shipping, why don't they make more warehouses overseas? (For example, I ordered a cheap webcam on Aliexpress for $2.50 including shipping... I got it in about 5 days)