BlueRidgeMark said:
Contractors who don't stand by their bids are on the same level as dishonest used car salesmen.
Yes you should try and stand by your word. There are higher responsibilities though.
Let's use your "used car salesmen" analogy. Say someone is interested in a car you are selling, and you agree to sell for $5,000 as long as you fix a little annoying noise. The $5,000 price is agreed and everyone is happy. Now the mechanic says that the little noise is a big end bearing, and it will cost $2,000 to get fixed. You were only going to make $500 on the car in the first place.
So, what do you do? Do you ask the mechanic to perform a quick and dodgey fix to get rid of the noise for a little while? Do you ring the customer and discuss the situation openly? Or do you just take the $1,500 loss on the deal? (No holidays for your kids this year). If you decide to be open an honest about the car, and the buyer backs out of the deal, what do you do then? Do you tell the next potential buyer about the problem? Do you get the car fixed and try and sell it for $7,000? Or $6,500? Or less?
It is a complex world, and often keeping rigidly to "your word" can be an excuse for less than ethical behaviour.
Let's get back to an example related to trees. Say you agree to remove a seemingly solid tree in a homeowner's backyard for $1,000. Once you have started the work, you discover structural problems (cracks, rot, whatever) that were not apparent from the ground. It is now your professional opinion that further work on the tree without the right heavy equipment risks serious damage to the house. Because of the location of the tree (backyard) getting the right heavy equipment in requires the removal (and hence replacement) of a fence. It's now a $5,000 job.
Do you:
1. Give the tree removal your best shot without extra help? Maybe you'll get lucky and the house won't be damaged, but you will have exposed the homeowner to additional risk that they didn't agree to.
or
2. Discuss the situation with the homeowner, and then do the job properly at a higher price (maybe you get nothing for your time, maybe you charge $4,000?)
or
3. Something else entirely?
The world isn't simple, the world isn't black and white. Try and do the right thing by your customers. Try and do the right thing by your staff. Try and do the right thing by your family. Always standing by the letter of your word is too often an excuse for screwing other customers on other deals.