Could your friend arrange his/her own quote of just one bathroom ventilation fan (his or her own) and see how that compares with the quote that has been provided for all of the vents?
There may be fire safety requirements that mean this is not simple. Or it could be the usual story of everything costing more in strata because strata is seen as a honey pot. Some lot owners in my building recently had recessed lighting installed without approval. When the Committee found out, it asked for a Fire Safety inspection to ensure the ceiling penetrations were done in the proper way. The recessed lights had been installed by a licensed electrician, but they didn’t meet some fire safety standard or other. So they all had to be removed and the holes sealed up and re-inspected. Big cost to the lot owners.