This is an age old question that's been around since TFP/CD first started. And there is still no definative answer. Some photographers still take images the old fashioned way, with film and paper, and so tend to provide less in the way of images, than digital users.
Some togs give out every photo they take, unedited. Some edit the best and only release them. So, there is no way to say what is average.
Best thing is to ask the tog before the shoot what you'll expect to get, and negotiate with them until you're both happy.
(Oh, and if you fancy a TFCD shoot sometime, just ask
Some people are like slinky springs - essentially good for nothing, but still raise a smile when you push them down the stairs.