I have always worked under the assumption that we work on a 10:1 scale. 5000 "units" of human cargo would be 500 people or so. So 2.5 million cargo of refugees would be about the population of Toulouse.
Then again, even 500 people sounds like a lot, so maybe it is better to say 100:1, 5000 units is 50 people. Hmm, too low?
How about 50:1, 100 people for 5000 cargo. Or 25:1, for 200 people. Under the 25:1 formula, a freighter with 500 cargo would haul 20 people, which sounds realistic considering the size of a freighter relative to the pilot flying it.
The funny thing is, is that Cruise liners inRL tend to carry as many as 3000 people, so it is not crazy to suggest a purpose built people carrier could haul a lot of people in space - in this case, the above scale would fluctuate depending on the type of ship. Considering that most people fly around 5kers and not liners to haul people, we can say that "people" being carried is quite low as a result of being a poor fit, with the rest of the haulage room being allocated to personal belongings and valuables, or for Toulouse, everything not nailed down.