I was talking with someone funding his own Abiraterone.
The generic is much less than you mention, but although he's being treated on the NHS and his NHS oncologist approves of him having the Abiraterone (and thinks everyone in his situation should be getting it), but he had to find a private oncologist to prescribe the Abiraterone. Initially he had to have 2 weekly blood tests and consultations to make sure his liver was handling it OK. This worked out around £1000/month for the drug and private tests and consultations. I haven't asked him recently, but I believe the frequency of tests and consultations reduces when it's been established the body is coping with it OK.
If you went this route, you might not need as much testing, given you've been fine on it for 4 years already.