Think about this a minute. How would you feel if when your city was building a school, they went to one general contractor, asked for a price, and paid whatever he asked?Interesting point Splatz.
People are asking for my time and resources, in the same way, they ask their grocer, utilities, and auto repair businesses for services. Why should I have to be the only business they "negotiate" with?
(Bad example, @Southeast Power would get the generator install and more than pay for any overspend of his tax dollars. But you get my point.)
Construction and trades are nothing like retail businesses.
Retail businesses like grocery stores don't negotiate, but all retailers sell identical products. People look at the price of beans at Kroger versus Publix and buy red beans at Kroger and black beans at Publix. People shop the hell out of them. To survive they advertise loss leaders hoping people will buy some products that are profitable while they are there. Retail is a tough business.
Automotive shops are a little different, but they still base their pricing on either flat rate for oil changes, alignments, etc., or a base shop labor rate and the book value for the time. Their book is very generous with the labor time estimates that they base their pricing on. The finished product is pretty standard with mechanical work. They do trade on customer service and trust and amenities like wifi in the waiting area. People beat them up all the time, they want them to match tirerack.com tire prices and etc., especially with new customers.
I have an idea what tires cost because I've bought hundreds of them. I don't shop when I have to buy tires, I have a guy. Occasionally I will sanity check his prices when I hear what someone else paid or see an advertisement or something, but I know he's OK. (That's actually a fictitious example, my tire guy is a really good old friend, and undercharges me drastically as I do him, but I'm making a point.)
The average residential consumer electrical customer probably buys electrical construction or service once every 10 years. No two people bidding will do even the simplest job the same way. It's not commoditized at all. When I put a new furnace in my house, I am going to shop.
Again, construction and service trades are nothing like retail. People shop. Be glad it's not a commodity, that's also why you can distinguish your work as better and more valuable so people will knowingly pay more for you.