The cost of converting a refrigerator to a toolbox depends on the type of refrigerator and the desired attributes of the toolbox, but much of the work can be done using simple tools. For simple conversions, the total cost might only be a few hours of time.
It's important to handle the refrigerant lines legally to avoid large fines. Refrigerators generally use Freon gas as a refrigerant. Freon is slightly toxic, but it also poses a significant threat to the environment. As a result, state and national regulatory agencies often forbid people from cutting refrigerant lines, so owners looking to fully convert a refrigerator to a toolbox might need to hire a Freon-removal expert.