Using age as the determining factor as to whether or not he needs the machine is completely irrelevant. I can only presume that this kid isn't the typical teenager, and his demeanor demonstrates this.
15 = freshman in highschool
How are his needs greater then anyone else interested in graphics or gaming? Those operations can be run smoothly on a much cheaper machine.
I want to point out this is over the top for a few reasons.
The OP is young. He doesn't have a job. This machine is a learning tool and a toy essentially. Graphic design, gaming and listening to music can all be accomplished on a much cheaper set-up.
Look man, I know your parents are well off and you received inheritance, BUT you should ask yourself some more questions before dropping 4k on a computer.
1. What if my computer is lost or stolen? Can I replace it? Can I afford to replace it? If no, then you need to reconsider.
2. Can I do this cheaper and put more in savings? 15 means he has not been exposed to any financial strain. What about a car when he turns 16? Gas? Insurance? Girls? Going on dates with girls? Paying for them? Buying other items (Xbox, Jeans ect)? Replacing those items if they broke? Rent? Food? COLLEGE!!!!!!!!!!!!???? Beer!?!?!?!
3. Do I have a steady stream of money coming in? meaning, about how much money will I have a year from now?
I have been out of college a year because I can't afford it. I have been working full time and have loaned everything i made (minus 2k I invested in the stock market in October and about $500 left in my account )to my mom to stay in the house we live in since she is a Real Estate agent and the market is a joke. While I can admit I am jealous of those who are more fortunate then I, I am very fortunate and happy with what I have. I know people who are a lot worse off.
Soon, my mom will sell an investment property and I will be paid back. I will then purchase a MacBook to replace the 4 year old Acer I bought when I first started College. I can only warn those who are young to save up every dollar they can. Unforeseen expenses are REAL and you need to be ready for them. Most young people do not plan for them at all, and then are in debt most of their lives.
4K on credit with a 20% Apr means you could be making minimum payments on that loan for YEARS. It's crazy how things work.
Now I realize this kid has the money right now, but he hasnt proven that he needs to spend so much of it.