Liquidated damages and sharing the pain

It is sometimes fruitful to peel an onion. It is also sometimes vegetate-able. With this aphorismic pun in mind, let's peel the onion of penalties.
One thing I learned two years ago and have been reminded of recently is that liquidated damages clauses are unenforceable unless they are an approximation of actual damages in a setting in which precise damage determinations are difficult to determine. So, for example, if I contract to sell you my apple for $1, a court will not enforce a provision in the contract that says I must pay you $5,000,000 if I do not have an apple to give you in exchange for your $1. Intuitively, this seems like a reasonable doctrine--I've only caused the harm of inconveniencing you in having to find another apple dealer, so its unfair that I should have to overcompensate you for this inconvenience.
But this doctrine has troubling implications. Does my promise to pay super-high damages count for nothing? We were both free to enter into this unfair contract; isn't this just the free market at work? Don't we have the fundamental freedom, as Americans, to enter into whatever contract we want? One could argue that the $5,000,000 apple example is an unfair contract, so we shouldn't be able to enter into such blatantly unfair agreements. But what's unfair about it? Both parties are aware of the consequences and are under no duress or fraudulent influence when they agree to the contract. If someone wants to promise to do something stupid, who are we to stop him/her or judge it as unfair?
The real value of liquidated damages comes in when performance under the contract has idiosyncratic value to one of the parties, above and beyond the market value of such performance. For example, if I want to recreate a special meal for an anniversary celebration, then the damage caused by the fishmonger selling the last lobster, which i had reserved and paid for in advance, thereby ruining my special dinner, will be much greater than a refund of the lobster. In fact, I would accept nothing less than $100,000 in exchange for that special lobster dinner on that one special night. So why shouldn't I be free to make a contract with the fishmonger that he has to pay me $100k if he doesn't provide the lobster on time? Or would this fall under the category of approximating a difficult-to-determine set of damages? What's interesting to me about this topic is how it pertains to credit card penalties and debit card overdraft fees. Financial institutions make money, in part, by charging higher interest and imposing fees on those who are just one day late in making a payment or who go $1 under the account balance. This is not a damages remedy; rather, it is a business model. To be continued...