Consideration is a central requirement of a valid contract. Consideration in the broadest sense is “accrual to one party of some right, interest, profit or benefit or some forbearance, detriment, loss or responsibility given, suffered or undertaken by the other.” Shelley v. Portland Tug & Barge Co., 76 P2d 477 (Or. 1938). Normally, consideration is pretty straightforward — you pay the guy at the farm stand a few dollars, and he piles some corn in your car. You get vegetables, he gets money. Exchange complete.
However, consideration can be more complex than just a movement of money. A person can incur a detriment at the promisor’s request and still create a validly considered contract. If you offered your bagpipe-playing neighbor $100 in exchange for him not piping at all hours of the night, you still have a valid contract even though, on paper, you have not gained a thing. The fulfillment of your prohibitive request is consideration enough. This is part of the reason why a Right of First Refusal or a Right of First Offer works as a contract despite only one party “getting” something tangible out of the agreement.
One point worth noting: promises made by parties after a contract has already been created will typically be unenforceable unless they are supported by new consideration. McGrath v. Electrical Const. Co., 364 P2d 605 (Or. 1961). Even if the consideration is nominal [minor], it must still be there for the contract to be properly wrought. Courts will generally not look into the adequacy of consideration and assume the parties are doing some sort of exchange that is sufficient to support the contract. Biersdorf v. Putnam, 182 P2d 992 (Or. 1947). Consider the classic situation of a contract where the price is being amended downward after a bad inspection. The Seller is foregoing money in exchange for Buyer foregoing a termination. Everybody gets something. However, when the disparity in value indicates that the consideration is a mere formality, courts will consider that “illusory consideration,” and it does not support the contract. Restatement (Second) of Contracts, section 79 (1981). For example, “I’ll give you $50 if you give me $500!” is clearly illusory consideration because the parties are exchanging fungible money at unequal rates, implying legal sketchiness.