One-off and prototype share similarities in development methodologies. But not in the long term goals. In a one-off I don't care about a few output errors that

One-off and prototype share similarities in development methodologies. But not in the long term goals. In a one-off I don't care about a few output errors that I can fix by hand once. Good enough is enough. A prototype requires to explore the limitations and estimate the effort required to eventually reach correctness. This estimate juggling time, cost, motivation, knowledge and "human resources" together.