The cost is the money you spend making the purchase plus any indirect costs (such as training costs) related to the purchase. The ROI is a calculation of financial gains or benefits that you obtain due to that cost.
To determine ROI profitability, there is a simple formula you can use. If the purchase yields a positive return, it can be considered profitable. However, if the purchase does not earn back the money it costs, it would be considered a negative return on investment.