What fascinates me most is that
7k people take up a *lot* of space.
Realistically, Cazador can exploit events that result in waves of refugees. If they have family, people will assume they just didn't make it. If you go to an authority, it can be easily written off.
It doesn't take many corrupt guards to set this up. Just don't count how many people enter the city. Or, have your corrupt guard lead them to "a camp for refugees", human trafficking 101. You can even have the absolute cult be in on this! Gain Cazador's support through calculated terrorism.
That being said... it seems this value exists because "set 10 vampire spawns free in the underdark" may be a lesser evil, but 7k really makes you think. At the same time, given our available responses to ascended Astarion... Larian seems to expect us to be shocked that he changed.