Dear Krishnan,
Various bloggers have given you responses that you can base your answer on. Aussiejohn has raised a vaild question, to which I will add some of my own as my wont.
Are you a student that has been set an assignment? If so, what course are you doing and what is your background? It is preferable for students to say what they think should be the answer and then seek comments on the answer to polish it. If you are going to base your answer on the comments made here, it would be appropriate for you to give a link to this site and mention that you have developed your answer based on peoples comments. That would be the most ethical thing to do to avoid committing plagiarism.
As someone pointed out the income from selling a light bulb is a one off, unlike selling a car which genrates income from offering services and the need for spares, etc. As the cost will be low when compared to the cost of equipments, such a long life only helps compete. When our lifespan is much shorter than that o the proposed item, do you think peole will rush to buy that if it is more expensive than the alternatives available? Kindly put on your thinking cap and consider what you would do and also ask your friends and relatives a hypothetical question (That's what the question posed is.).
Have a nice day.
Simhan