Considering that the verb “milk” in English often refers to an intellectually dishonest manner in which one tries to extract the maximum financial (or otherwise) gain from a given situation over an extended period, how about:

Tu obéis à ton chef au doigt et à l’œil. Et ce, uniquement pour qu’ils puissent s’en enrichir / s’enrichir toujours plus.

I might go for « tirer le meilleur parti d’une situation » in a different context, but as you seem to be talking specifically about monetary gain here, this phrase would sound rather vague, falling short of conveying the monetary nuance.

Ideally, if I could replace « s’enrichir » with its more casual counterpart, more in keeping with the informal tone of the verb “milk”.

I suppose the closest French expression is “tirer profit de [la situation]”, in which “tirer” (“draw”) is used similarly to “milk”. This expression can be used in formal language. I can’t remember any slang variation to it.