If your estamate was only $100 then you should only get $100 unless they added work to the project.
It is unfair business practice to estamate $100 knowing it will cost more just to get the job then jack up the bill after the fact that type of stuff really angers customers myself included and wiil give you a bad reputaition because they will spred the word .
First the customer does not know how much something will cost till you give them a quote and you must sell the job on the spot if you leave without the green light you have already lost the job because the next guy that comes over may low ball just to get the job then jack up the price at the end.
So the price you give must be high enough in case of trouble so you will still make money but you must keep your word on the price you gave otherwise they will not tell their friends they found a great Electrician.
I don't estimate $100 knowing it will probably be more. I will estimate $200 knowing it will likely be less. When that $200 estimate turns into a $125 invoice they are happy. If that $100 estimate turns into a $250 invoice (and there was no work outside of orignal scope) then they are not happy - and understandably.
If it is a written estimate it is likely to be more accurate. If they want to know a set price more time is needed to know what it will take otherwise a high number is needed just in case. Most cases I am talking about are small repairs or installation of specific items. New construction or major rennovations is a little different. 99.99% of those jobs I run into the customer does not even know what they want - a few basic things, yes, then you start mentioning optional items and they didn't even consider those prior to you bringing it up.
Around here I get plans for new homes or additoins handed to me all the time, and they want to know how much to wire it. No electrical detail at all on the plan. Those are times when you would just like to give them a price range of "anywhere between $5000 and 100,000 should cover it. Give me some details of what you want and I can get a little closer.
This is sound advice and a principle that I have always worked off of. "Sometimes you eat the bear, and sometimes the bear eats you" comes to mind. Very rarely should the bear end up eating you though. :slaphead:
The auto industry probably has the hour book down better than anyone else, 10 hour book job takes 4 hours, until you run in to those rusty bolts.
The auto industry is a little more predictable as far as what work is required to accomplish a particular job. It takes about same process to replace brakes on several models. Putting a receptacle in a building can require about as many different procedures to do so as there are different buildings to put it in.
When they do flat rate pricing for automobiles they do take into consideration what vehicles apply to the pricing. Some vehicles do fit into a different rate. Take my diesel truck. I would take it anyplace for a $30.00 oil change - but the 30.00 deals always excludes diesels in the fine print. The cost of oil alone is more than $30.00 if I change it myself.