bikramjitkar, calm down.
No need to be so rude.
Just because he got a 25k phone at the age of 15-16 doesn't give you the right to speak in this manner with him. He didn't force his parents into buying the phone for him.
It doesn't matter how much you spend as long as you're not wasting what you spend.
2 years ago 25k was pretty much the mid tier of high end phones except apple (usually prices didn't go above 35k for phones other than iPhones). Apple is to blame for the inflation, not parents.
If the other person has said and explained that he can indeed use his phone to the fullest, you have NO REASON to attack him for spending so much cash.
I think it is absolutely fine to reward your child at that age if he has worked hard and earned what he has been gifted. Do you expect a 16 year old to earn 25k in ~3-4 months? Are you out of your mind?
If he was doing what he was supposed to at his age, you have no reason to say what you did to him.