Which pricing approach involves allowing the buyer access to the supplier's financial records?

The correct choice refers to a pricing approach known as open book costing. This method allows for transparency between the buyer and supplier, as the supplier discloses detailed financial records, including costs related to materials, labor, and overhead. This level of transparency helps the buyer to understand the true cost structure of the supplier's products or services.

By sharing financial data, both parties can engage in discussions about cost management, efficiency improvements, and ways to enhance value for both sides. This fosters trust and collaboration, as both parties have a clear understanding of the cost implications tied to their business relationship.

In contrast, while incentive-based pricing, gain-share pricing, and shared risk-reward pricing may involve some elements of collaboration or cost sharing, they do not typically require the same level of financial disclosure as open book costing. These methods focus more on aligning incentives or sharing the benefits or risks of financial outcomes rather than providing direct access to financial records. Thus, open book costing stands out due to its fundamental principle of transparency through access to the supplier's financial information.