$2000 reasonable estimate to install new 3 unit buzzer entry/intercom system?

Hi Brownstoners, the existing buzzer entry system in our 3 unit home is malfunctioning (works only sporadically, and each unit is experiencing the same problems) and we received an estimate of $2000 to replace it – without any electrical work in case any major work is necessary. I’m not even sure it needs to be replaced, but the vendor claims that troubleshooting it and repairing it, if reparable, will likely end up costing something similar ($150 per hour for the technicians, a minimum of 3 hours). Does this sound reasonable? I was hoping for a repair bill for a few hundred bucks, not to have to spend $2000 to replace the whole thing.