Computer-implemented methods and computer systems for offering vehicles, which are subject to sale agreements between sellers and buyers, on online markets and soliciting additional offers for these vehicles by third parties. This additional offering may generate additional revenues, above the agreed upon prices between the initial seller and buyer, and these revenues can be shared by sellers, buyers, and service providers. For example, a seller may contract with a dealer to sell a used car for a certain price, which may be a part of a trade-in transaction. Information about the car, including a price, is then posted on a website. Third parties may view this information and post their offers, which are higher than the initial contract price. The new higher offer may be accepted and the proceeds may be shared by sellers, buyers, and service providers.