Proton therapy is not cheap, but it is my understanding that most major insurance companies cover it. The part you are responsible for would depend on how good your insurance was. Medicare also covers it and if you have supplemental, I would assume the supplemental would pick up the difference. I don't know for sure because my insurance paid it in full, but I have heard from others that it is about $60,000. Also have heard that the amount billed insurance companies is more than that billed to Medicare - don't know??
Without insurance the cost in 2004 was about $38,000 with $8-9,000 down payment. I think monthly payments at that time were about $1,000. This is what 2 men we referred to LL paid in 2004 as they had Kaiser and Kaiser will not pay for anything they don't do in house.
The above is an "in the ballpark" answer, so don't quote me without checking with Loma Linda directly.
I also should add that the above only refer to Loma Linda - I have no knowledge of the cost at the other institutions that do proton.