The relationship the firm has with its clients and suppliers largely determines the amount of value it is able to capture in the chain. Yet little is known about the impact of market uncertainty on the choice of the best buyer-supplier strategy in terms of value appropriation. The paper proposes to investigate which among different types of strategies bring more value to the buyer when market uncertainty increases. It relies on a very innovative method of multi-agents simulation based on an in-depth ethnographic observation phase of a real market in France. It shows that pure loyalty is not necessarily the best strategy when market uncertainty increases and that the buyer may face a dilemma between maximizing the margin rate and ensuring regularity of supply.