This study investigates whether market experience eliminates the endowment effect, a market anomaly where individuals value items more highly once they own them. Field experiments in two well-functioning marketplaces—sports memorabilia trading at a sportscard show and collector pins at Walt Disney World—show that as market experience increases, individual behavior converges to neoclassical predictions. Experimental results indicate that market experience significantly reduces the endowment effect, with experienced traders showing negligible endowment effects. These findings are robust to institutional changes and extend beyond the studied markets. The study also examines whether the endowment effect is due to treatment (market experience) or selection (pre-existing preferences). Follow-up experiments and panel data analysis confirm that market experience reduces the endowment effect, with experienced traders showing no significant disparity between willingness to accept (WTA) and willingness to pay (WTP). The results suggest that market experience eliminates the endowment effect, supporting neoclassical theory. Additional experiments in different markets and settings further validate these findings, showing that trading experience reduces the endowment effect. The study concludes that market experience plays a crucial role in aligning individual behavior with neoclassical predictions.This study investigates whether market experience eliminates the endowment effect, a market anomaly where individuals value items more highly once they own them. Field experiments in two well-functioning marketplaces—sports memorabilia trading at a sportscard show and collector pins at Walt Disney World—show that as market experience increases, individual behavior converges to neoclassical predictions. Experimental results indicate that market experience significantly reduces the endowment effect, with experienced traders showing negligible endowment effects. These findings are robust to institutional changes and extend beyond the studied markets. The study also examines whether the endowment effect is due to treatment (market experience) or selection (pre-existing preferences). Follow-up experiments and panel data analysis confirm that market experience reduces the endowment effect, with experienced traders showing no significant disparity between willingness to accept (WTA) and willingness to pay (WTP). The results suggest that market experience eliminates the endowment effect, supporting neoclassical theory. Additional experiments in different markets and settings further validate these findings, showing that trading experience reduces the endowment effect. The study concludes that market experience plays a crucial role in aligning individual behavior with neoclassical predictions.