how on-target have you found estimates to be?

when you hire a company, or worker, to do a project in/on/for your home and you get an estimate prior to hiring them... once the work is completed, how close to the estimate is the actual bill? have you ever received an estimate that was significantly over, or significantly under the amount of the final bill?
yesterday was my first experience where the estimate was no where near the final cost. we had brickwork done in the front of our house: a retaining wall, a small flower bed next to the front steps, and a flower bed around a tree. when they came to do the estimate, they gave us the pirce but what was included was a semi circle around the tree. when we booked, i explained that we would prefer a full circle around the tree and they told me no problem, they would tighten it up and do a full circle - the final cost may be just a couple hundred dollars difference at most.
well, i had to go to work yesterday before they finished the work, but when dh texted me the final price, i almost - $700 more than the estimate!
granted, they were wonderful to work with as a company - went to new jersey to get the bricks i wanted, showed up on time, were fast, and the work is gorgeous, exactly what i wanted - no complaints there. but i'm really unhappy with the difference in price, i feel like they should have warned us. when i hear a couple hundred dollars, i figure 200. maybe 300. but 700?!
what do you think? experiences?

Re: how on-target have you found estimates to be?

How big is this circle? that seems really high! Unfortunately, you always have to discuss $$ before you proceed on any job, regardless of whether or not the contractor says "okay, no problem."

I've had certain things come up while in the midst of contractors doing work. But $700 to finish up a circle seems high to me.

Re: how on-target have you found estimates to be?

thanks for your reply... anyone else?