only expensive clothes have reproducible sizes. You can test this yourself. Go pick out 3 different levis jeans that are the same size that ought fit you, in different colors but the same cut. They will all fit slightly differently.

Expensive clothes that are meant to be altered will usually have better tolerances, at least in my experience.

this is one of the main reasons i refuse to buy any clothing intended to be worn outdoors from amazon, shein, aliexpress, ebay, &c.