Here in New Zealand, I've charged out jobs as the Electrical Contractor, in terms of Materials and Labour, as a full price.
I don't care what anyone says, I have my own Spreadsheet, that I update myself with local prices.
Or at least I did when I was in the "know".
Main Contractor here would say, give us your "best price".
I'm giving him the best price, try and get my services for less, with the same quality job?.
One thing you people have to realise, is that your Contractor is paying for your expertise and the best way to do things, therefore it should take you less time.
It's not a labour only thing!.