All insurance contracts or contracts for health care services of a health maintenance organization purchased by the Kansas turnpike authority pursuant to Kan. Stat. Ann. § 75-4101, and amendments thereto, shall be purchased by the authority in the manner prescribed for the purchase of supplies, material, equipment or contractual services under Kan. Stat. Ann. §§ 75-3738 to 75-3744, inclusive, and amendments thereto. Any such contract having a premium or rate in excess of $500 shall be purchased on sealed bids.