He's stitching you up! (Sorry)

Think about it - $50 per hour gross. That's before tax, your time to prepare, edit, wear-and-tear of your equipment, transportation etc.

I'd triple it.

I shot a heart transplant it was shot on Beta SP. I found that the head surgical nurse was the one to win over. The secret is to ask (her or him) whenever you do anything. The doctor is usally the coolest one there. After a while (when everyone's cool with you) they will be telling you the best angles etc. Of course that was my experience. Your shoot may be totally different depending on the doctor and staff. The total shoot lasted from about 8pm to about 2am after they closed the patient. The doctor got all the clearence from the patient and family. I charged for a full day.

You should be charging (as a professional camera man) anywhere from $350 to $500 per 10 hr day for your labor. Then a camera package rental for DV or HDV anywhere from $150 to $300 per day plus tape cost. If you do a half-day (a lot of shooters don't do half days) then the industry standard is 60% of your day rate and full camera rental rate. Of course every thing is nego'ble
JM2C