1. A system, comprising: a plurality of computing devices configurable to implement a plurality of resource instances of a provider network; and one or more computing devices configured to implement a resource planner; wherein the resource planner is operable to: receive a plan request from a client, wherein the plan request comprises one or more job goals and an indication of a resource acquisition policy to be used to obtain one or more resource instances of the plurality of resource instances to be used for the job, wherein the resource acquisition policy specifies one or more instance data sources; and generate a resource acquisition plan in accordance with the plan request based at least in part on an analysis of pricing data obtained from an instance data source of the one or more instance data sources, wherein the analysis comprises one or more computation steps indicated in the resource acquisition policy, and wherein the resource acquisition plan comprises at least one recommended acquisition price for a resource instance of the plurality of resource instances to be used for the job; and provide an indication of the resource acquisition plan to the client.