Like others have said (oxonbeef), if you are wanting to argue over *future* revenue then just walk away. You're going to spend much more than $20,000 on legal fees, it'll easily take more than a year and there's a good chance that you will run out of money before they do. To be honest, it's a shame, but that's the American court system, buddy.
Whoever can afford to keep the case going the longest is generally going to win. This is why 'chilling effects' have been such a big deal recently.. If you write a bad review about my company online and I have a company lawyer.. I just have him threaten to sue you for tens of thousands, you get scared and remove the bad reviews. Or you fight it and I win by default because half way through the trial your attorney is going to be dismissed because you can't afford him anymore.
Now.. Another thing to take into consideration is how airtight is your contract? I know you say it's strong, but have you had an attorney check it out? Did you have an attorney write it? Otherwise, are you entirely familiar with the laws in place that govern this area? If you messed up on one key part of the contract, they may have spotted that and ended the contract because of it. An important thing to remember when you are writing a contract is that you cannot simply 'make up' your own laws. You can use the existing laws in place to protect your work/money.
Just because somebody agrees that if they violate my TOS, I can sue them for $20,000,000 doesn't mean I'm going to win a case for $20M when they violate. Because I'd sound like an idiot, citing pieces of my TOS in court instead of local/state/federal laws.
Another thing.. Are you local to them? If you are in N.Y. and they are in L.A., I hope you have a lot of money to fight this case.. Because it will be taking place in L.A. unless your contract states otherwise. A case must be heard at the local courthouse where the incident occurred. Since you are saying they breached your contract, the breach occurred in L.A. That may be another thing they are looking at.
Lastly, did you breach the contract in any way? Did you maybe promise white hat methods and unleash a SENuke X campaign or a bunch of Fiverr gigs?