Time for a new doc if this guy doesn't realize that 10ml in a vial doesn't equate to 10ml in your body. I'm VERY careful (I'm a cheap bastard) with my drawing and usage of conservation techniques, and still have yet to see a full 10ml worth of injections go into my body. That's probably the ONLY advantage of using the small 1ml vials - but screw paying 4x the cost because it's in a smaller container.
It's not likely that you're being ripped off, but you can always just take out 4 3ml syringes (they're cheap) and withdraw the entire contents of the vial and see for yourself. Going by weight is a tricky disposition as you would need to know the density of the oil/the hormone/and whatever else they put inside the vial (or specific gravity as mentioned above works).
My .02c