The most likely factor that cost a client in Grangere membership would be "Farms faced severe drought." This would impact the agricultural industry in the area and could lead to significant losses for farmers and clients involved in the agricultural sector, resulting in a decline in membership. The other factors mentioned, such as wheat prices declining, spikes and railroad prices, and variances in freight costs, may have some impact as well, but severe drought would likely be the most detrimental factor in this scenario.
