What type of negotiation strategy requires the supplier to open its books to the purchasers?

The cost-based price model is the correct choice because it involves a detailed examination of the supplier's costs related to the goods or services being provided. In this model, the purchaser requires the supplier to disclose financial information, allowing for transparency in the pricing structure. By opening its books, the supplier can present a detailed breakdown of costs including materials, labor, and overhead, which justifies the price being charged to the purchaser. This level of openness ensures that both parties can engage in a more informed negotiation, potentially leading to a more equitable pricing agreement that reflects the actual costs incurred by the supplier.

The other options do not involve this kind of detailed cost scrutiny and financial disclosure. The market-based price model typically relies on prevailing market rates rather than an in-depth understanding of costs. Benchmarking strategy focuses on comparing performance metrics with industry standards rather than scrutinizing a supplier’s internal cost structure. Competitive building aims at creating competitive dynamics in the negotiation process without necessarily requiring a deep dive into the supplier's financials.