I see a private Ob and his Pregnancy Management Fee was $1500 of which I got $479 back from Medicare, nothing from PHI. Each appt costs me $40 (which includes a scan), of which I get about $39 back through Medicare even though I haven't hit the threshold.

As Glenny said above, the amount of $500ish back from the the Ob fee seems to be standard no matter how much you pay.

After we did IVF last year, we hit the threshold and we were getting 80% back from GP appts etc through Medicare.

You're right though, PHI doesn't impact on the fact that you are seeing a private Ob... it seems to only help with the hospital fees (usually paying the excess only of admittance). Mine didn't help a great deal with the anaethetist fees when I had my laparoscopy. From memory, I paid about $700 up front and got about $200 back from Medicare and about $50 back from PHI... I shouldn't complain, because at least I got something back!