The Internet of Things (IoT) is steadily growing and migrating to decentralized architectures. In this context the Swarm approach, based on organic, edge-centric IoT networks, proposes one step further toward cooperation among devices, through the creation of a communication mediator called Swarm Broker. An important aspect in creating a cooperation network in the Swarm is the economical domain: the Swarm economy that guarantees fair rules to stimulate resource sharing among participants. This economic aspect is even more challenging in networks with distributed governance and motivates the adoption of a technology for a trustworthy and immutable public registry, such as blockchain, to store transaction information. In this paper, we aim to create an economic model that regulate the cooperation among the participants of the Swarm, by implementing strategies, to fulfill the restrictions posed by the decentralized network and the presence of resource-constrained devices that integrate the Swarm. We created a microeconomic model for resource sharing in the Swarm and a transaction model, based on the price and reputation of participants. We created a blockchain-based system for storing currency, contract, and reputation information in a distributed way. We included the resulting models and implementation into the Swarm network, by adding a module into the Swarm Broker.