Chris Seferlis gives us the details on how Azure Data Factory V2 pricing works:
2. Volume of data moved – this is measured in DMUs (data movement units). This is one you should be aware of as this will default to auto, which is basically using all the DMUs it can use and this is paid for by the hour. Let’s say you specify and use 2 DMUs and it takes an hour to move that data. The other option is you could use 8 DMUs and it takes 15 minutes, this price is going to end up the same. You’re using 4X the DMUs but it’s happening in a quarter of the time.
This is good to look at and do some comparisons since how many DMUs you’re using is where the bulk of your spend if going to be.
There are a few moving parts here, so the calculation is not trivial. But Chris makes good sense of it all.