The work I do is fairly specialized and takes me a relatively predictable number of hours. Sometimes I'm wrong and it takes me more, but a good amount of unpredictability is baked into my charge.
If you charge more for a fixed cost, then it doesn't really matter if you are off 3x one time. Yes, it's annoying, but you make up for it with the majority of times where you work the estimated number. If you are consistently underestimating, then you need to up your estimates.
If you charge more for a fixed cost, then it doesn't really matter if you are off 3x one time. Yes, it's annoying, but you make up for it with the majority of times where you work the estimated number. If you are consistently underestimating, then you need to up your estimates.