Hey there,
Im very sorry to hear about your sons predicament i beleive the biggest reason that testicular transplants are not available is not necessarily because they wont take but because the sperm cells that would be generated would not be genetically the same.... essentially the childeren fathered from your son with the transplanted testical would technically be genetically the offspring of the man who donated the testicles. this tends to create a lot of moral/ethical questions. it is also possible that the testicles would not take because they dont last long without blood flow making transplanting difficult.
I too am sorry about your sons loss.
Not to make it sound like a money issue but, as to the financial cost, if he had a testicle transplant he would be on rejection drugs for the rest of his life.
For him, prosthetic testicles and the hormone therapy can help him with his body image. He should be able to ejaculate normally as well, yes he's sterile however. He should also be able to maintain his hormone levels.
Lastly, don't give up. There are new advances happening all the time.
Thanks for the impute, I completely agree.... like Dan said there are always new advances in science and medicine and many people end up living normal or close to normal healthy lives if treated with hormone therapy and prosthetic testicular implants can greatly boost a guys confidence and self esteem.