The reality is that there is generally a lot of leeway in "fair" as far as contracts go. You can definitely sign an intentionally adversarial contract and it will usually hold up. I have only known courts to nullify contracts when they specifically violate a given law; for instance, a contract where one side can kill the other side in event of breach would not be valid because it runs afoul of murder/assault laws. However, a contract where an exorbitant fee is levied upon one side in event of breach would generally be held as long as all parties were deemed capable of understanding the contract and endorsing it by their own free will (i.e., not under duress) when it was signed.

IANAL, this whole post may be and probably is wrong. Please correct me.