Depending on the class of the protein, the yield could vary hundreds of folds in a normal range.
Microbial: several mg/L to hundreds of mg/L;
Baculovirus: 0.5 mg/L to dozens of mg/L;
Mammalian protein: 0.3mg/L to several dozens of mg/L;
Mammalian antibody: 5mg/L to 1g/L.