Willow biomass presents a promising feedstock for biofuel production, but its economic feasibility depends largely on feedstock availability and cost. This study investigates the relationship between landowner participation in willow biomass production and its impact on the minimum selling price (MSP) of both willow feedstock and bio-oil within a biorefinery framework. Using EcoWillow 4.0S for feedstock cost estimation and SuperPro Designer for process modeling, the analysis evaluates MSP variations across different participation levels based on data from five counties in Northern New York State. The results reveal a strong inverse correlation between landowner participation and MSP. As participation rises from 1% to 5%, the MSP of willow feedstock drops from $98/Mg to $90/Mg (8% reduction), while bio-oil declines sharply from ~$21/L to $4/L (over 80% decrease). However, beyond a 20% participation threshold, further reductions in MSP plateau, indicating the realization of economies of scale. These findings suggest that increasing landowner engagement can significantly lower feedstock costs, thereby improving the economic feasibility of biorefineries.