First off I am not in the security or alarm business, however I was a small business owner for 30+ years. It is NOT the $2 plastic cover he paid $150 for, it was the time, transportation, gas, labor, insurance, unemployment ins. advertising, etc. to own and run a business. When a Company sends a repair person or tech to your house, they need to be trained, knowledgable in what ever field they are in. If your friend was charged $2 for the battery cover only, the company would be out of business in weeks. Businesses are in business to make a profit - yes, that almost sounds like a curse word these days, but that's why people take the risk.
The flip side of the coin is these businesses pay taxes, support schools, police, hospitals, etc. They also support all the ancillary businesses they get their supplies from and so it is not as simple as many think. They support the Deli's, pizza joints and hamburger joints around their businesses that they eat at. Believe me, after running a successful business for 30 years I know for a fact that employees, customers and the Gov't THINK that 95% of the incoming money a company earns is profit - NOT SO! National statistics say that most small & mom and pop business make between 10 and 15% profit after expenses. Many larger business make even less of a percentage. That means that 85%-90% or more of all the money they worked their butts off for goes somewhere's else.
I'd bet the company that sent a repairman to your friends house does not think he charged too much. BTW, I do not know if ADT is a franchise or company owned but if it is a franchise then the owner /operated must pay ADT a franchise fee on top of all other expenses. I am just pointing these things out as many who were never in business for themselves are totally unaware of all the expenses a business incurs. The other interesting statistic is that 90% of start up business fail in the first 2 years!! Not very good odds to risk a ton of money on when it's your hard earned money.
I only wish I made even close to what my employees and customers thought I made - most don't have a clue! Being in a legitimate business today is very difficult and as hard as it once was years ago, it's even harder today.