Amazon offers its Amazon Prime members the Master Lock Biscuit Privacy Door Knob
in Polished Brass, model no. BCO0303, for $6.26
with free shipping
. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs $5.73.)
That's the lowest total price we could find by $13. It features an antimicrobial finish.
Amazon Prime membership is $79 per year; however, Prime is free for college students for one year, and free for parents and caregivers for three months.