Yes, it is costly. But analysis shows that organ transplants are financially worthwhile.
Kidney transplant, an example:
The treatment of a kidney patient who is on dialysis 2-3 per week costs 500,000-700,000 NOK per year. A kidney transplant costs 300,000 NOK in addition to medicines that cost 80,000NOK per year.
Moreover, a person who has had a kidney transplant will most likely return to work, unfortunately this is not possible for most patients on dialysis.