ADR Fee how to calculate

[KenG]

I live in Japan and I am quite sure that no insurance cover the ADR surgery abroad for me.

what I would like to know is what makes differences of fee when one person have same one level ADR by same surgeon.
I know it makes difference between l4l5 and l5s1 surgery but I think I saw some differences of fees even one same level ADR by same surgeon in ispine messageboard here.
25000 euro ? (u.s.dollar) to 45000 euro (u.s. dollar )?

does the fee difference relate with difficulty of the surgery ? like age or condition of that one level disc ?

sorry for my english, but it might give some good info to foreign patients in near future where ADR is quite new and with no insurance coverage.