It depends on the condition. If my dog had a chronic condition (not likely due to this genetics). But, theoretically, if it was a painful, chronic condition and surgery would only help some ... but not much, I'd opt to put him to sleep. I don't think he'd be happy living in pain.
On the other hand, if it was a treatable condition that would go away with surgery or be alleviated ... dude, I'd pay any amount of money. If I didn't have it in cash, I'd use credit. If I didn't have enough in credit - I'd sell everything to pay for the medical bills.
My dog is ... I can't describe it. He's the best darn friend I've ever had. We're a team. He's never let me down and would do anything for me. He loves me without condition and without reserve. I can't get that just anywhere.
So, yea, I'd never give up on him.