Good morning. Thank you for the question.
Have you seen the new approved cost table? This is expected to be officially released in October 2018 as part of CDM 6.0. Please see details here https://github.com/OHDSI/CommonDataModel/tree/Dev?files=1 it has two key fields cost_concept_id and cost_type_concept_id. The later is for the provenance. This is a long table, i.e. each cost has it's own row record.
The current omop vocabulary is designed to support this unreleased version of CDM cost table.
If the cost record is to be linked to payer_plan_period, the current recommendation is to use either 31968 or 31969 or 31970 from here http://athena.ohdsi.org/search-terms/terms?domain=Type+Concept&vocabulary=Cost+Type&page=1&pageSize=15&query= in your use case above, if the patient has insurance and that information is in payer_plan_period , then depending on whether that insurance was primary or secondary - I would use either 31968 or 31969 for all rows corresponding to the insurance company, depending on whether it is primary or secondary.
If the cost record has no relation to payer_plan_period table e.g. uninsured/self pay - then we currently don't have standard cost type concepts. We will have to create some. Coat_type_concept_id is a required field.
Note: the new cost table has cost_concept_id that can represent a lot of different costs. http://athena.ohdsi.org/search-terms/terms?domain=Cost&vocabulary=Cost&standardConcept=Standard&page=1&pageSize=50&query=