Volley with them. Don't volley them too too high. But if you're the one helping them, and they can't do it themselves, tell them to save their money to at least half a bil, preferably more, and then drop volley inactives with them. Easiest way. Or just have them farm inactives.
I don't know the rest of the prices, either. But if you think about it, it'd be 512 mil to fill all dorms with t3 freshmen. To get them to t4, it'd be a higher price for each. 512 x 4 = 2,048,000,000 But it'd be more than that.
91k cs, costs 4.16 bil to buy all 32 ( if you do not already have any T3) and the amount for having the dorms, that also adds to it
18 dorms with level 4 T3s is just under 2.5bil..... so I'd say about 4.5bil is needed for T3bc as long as all dorms are already unlocked
I remember I needed 3.7 billion to get t3 bc but I also had to buy 1 or 2 dorms and I still had money left over