Writing a blank check for AVM surgery is something that almost none of us could do. Back in 1996 or so, Chari had several embolizations and surgery at Stanford. For grins mostly, since insurance covered all but a few thousand and our travel expenses to/from there, I kept track of the costs.
What insurance was billed was about $250K or so! What the insurance paid Stanford and the DRs was about 25% of that!!!!!!!!!!!!!!! I was so shocked by that figure that I went in to talk with our insurance rep. She looked at my data, and said "Yep, that's about what they pay."
Now you might be able to negotiate a deal, but that would be a nightmare in my mind with how many people you'd have to deal with, etc. I guess the other option would be just plan on declaring bankruptcy after you're cured, but I don't anything about that process.
It's absolutely critical that you have trust in your AVM medical team, whoever it is. We felt like we had exceptional care by everyone at Stanford, but I'm not trying to change your opinion. You feel how you feel.