I can't give you a percentage that would be remotely accurate.
If the compressor died, it could have been from being overworked; having to constantly re-fill leaky air springs, in which case, you'd need new air springs and a new compressor.
It might not be the compressor at all; it could be the relay. The relay typically sells for $40 on eBay. I think it's $90 for a new one.