It is cheap and profitable!
The development cost will pay off in less than a month!
The actual price depends on complexity of the project, and might be in the range from €1000 to millions, but some projects like update the information display system paid off for the customer in less than a month.
Sometimes a unique, even expensive, device can be paid off very fast. For instance a precision frequency voltage inverter was produced in several copies, but its use significantly reduced the repair time of diesel generators in the field. That brought a big advantage for companies involved in the supply, commissioning and connection of controllers for diesel generators.