A Plus Choice via eBay offers the Yescom HO Ventilation 6" Inline Cooling Duct Fan, model no. 23FAN009-6-400, for $52.90 with free shipping. That's $2 under our mention from a month ago and the lowest total price we've seen. (It's also a current low by $12.) It features a 353CFM airflow rate and 2490 rpm.