80 dairy cows for 2 guys would be full-time work.... If you are seeing larger dairies, they have more than 2 people working.  At one time, you could figure 40 cows per full-time man.  Those numbers have changed.  But the increased efficiency goes with larger herd size.  Which points to the thought that this farm has not been keeping up.

I would expect that 200 acres should be enough land to grow all the forages for 80 cows (and young stock), and at least some of the grain needs.  So, I think 600 acres is a lot more acres than is needed to support 80 cows.  That is true here, and I would expect it to be true in Wisc as well.  So, it seems to me that some of that land is being used to raise grain to sell- or it is not crop land.  If the dairy industry would be in better shape, adding more cows to better match available land would probably make the whole farm more financially viable. However, the dairy industry is not in that position now.  Maybe.... hopefully.... in the future....

To add more cows, on top of $5.8 million initial purchase price, is going to take a huge capital investment - as well as adding hired help.  Question is: can this son manage employees?  Not everyone is cut out for that.  I think the hand-writing is on the wall......