Software tools can be expensive. You have to factor in the cost of the tool, the hardware to run the tool on, and the training of your employees to use the tool. But consider the higher costs of not buying the tools. Lower productivity, higher probability of customer dissatisfaction, delayed product release, increased rework, poorer produce quality, etc.
Reference:
Huff, C., "Elements of a Realistic CASE Tool Adoption Budget," CACM, April 1992.
