Table schema:
CREATE TABLE table_name_90 (publication_date VARCHAR, person_s_ VARCHAR, reported_price VARCHAR, publisher_s_ VARCHAR)

Question: What was the publication date of the photos of Sean Preston Federline that cost $500,000 and were published by People?
SQL: SELECT publication_date FROM table_name_90 WHERE reported_price = "$500,000" AND publisher_s_ = "people" AND person_s_ = "sean preston federline"