A2M was valued at $400m because of its profitable fresh milk...

A2M was valued at $400m because of its profitable fresh milk business, it was making good profit, but was offset by loss-making in UK & US expansion, at that time its formula business just started picking up.

AuMake, might grow fast as a large retail business chain, but challenges are it's still retail with small profit margin (say improving from 13% to 15%), then Australia has very expensive labor costs (could hire students) and rental expenses, most important, director remuneration for any listed company is not cheap.
Chinese government is tighting up customs rules, Daigou would be much hard over medium and long term, imo.