In this paper we have described several ways that the Reactis tool suite provides significant added value to the market-leading MathWorks Simulink/Stateflow modeling environment. Through its sophisticated model-debugging capabilities, Reactis enables engineers to debug a software design before system implementation is undertaken. The earlier design errors are detected, the less costly they are to fix, so better model debugging can reduce overall software costs. We also discussed how the comprehensive yet compact test suites produced by Reactis can dramatically reduce the costs of checking for conformance between a model and system and of reverse-engineering a model from existing control software. By automating tasks that currently require significant manual effort, Reactis cuts development costs. By enabling more thorough testing and validation to be undertaken, it also enables errors to be detected and fixed before systems are fielded and therefore cuts recall and liability costs.