Programmatically creating computed field in field collection

I am programmatically creating a new node that has one or more field collections that have computed fields. Using code similar to Example: Programmatically create and update field collection with Entity API, the non-computed fields are correctly built. However, if I try to ->set() a computed field, I get an error that the field is "not writable." If I don't set anything, I get "Notice: Undefined property: FieldCollectionItemEntity::$field_labor_cost_sub_total".

I have looked at #1414282: Support for entity_metadata_wrapper(), but that seems to be for fields that don't store the value; I do store it.