Because I know later on he is going to have problems. I know from my personal experience. He is only 15. If his peers start passing him in height, one day he will ask if he is going to be tall. I would say no, it is too late. Especially for men this is important.
You are very frank to admit this.
I must stress: this is a dangerous surgery and obviously the safety of your child is paramount and takes precedence over mere money. Dr. Paley is generally regarded as an exellent surgeon with acess to modern and comfortable facilities, he is however perhaps the most expensive limb lengthening doctor of them all.
Dr, Guichet (who actually moved his clinic to Italy) also enjoys an excellent reputation particularly for his focus on athletic recovery which seems to yield excellent results. This includes a strict regime of physical therapy which can be very taxing, he is also very costly but not quite on Dr. Paleys level.
These are the doctors I know of but I'm sure there are alternatives. Though wherever you go expect the surgery to be costly, painful, time consuming, and more or less dangerous.
Wish you and your children luck. Remeber to research and to never compromise with safety.