Too often, we have people call us and ask (no joke), "I want a web application ... how much does something like that cost?". This is akin to asking how much a house will cost without describing the number of rooms, bathrooms, garage, land, windows, square feet, light fixtures, etc. However, software development is even more complicated. A lot of questions need to be answered before the exact cost of a project can be known. To best illustrate this, we often refer to the Cone of Uncertainty. First discussed by NASA, it illustrates why in complicated projects, the true cost is not known until the project is complete.
In the beginning stages, the estimate can easily be off by a factor of 4x. This means if you intend on getting estimates for development and the estimates range from $30,000 to $120,000 it is not abnormal. Even when the requirements and user interface design is complete, the estimate can still be off by a factor of 25%. Unfortunately, software development is a complex effort. This is why we advocate smaller iterations and a more agile approach to application development.