$148 for used/refurbished units on eBay to over $1500 or even $2600 for new surplus or in-stock units from distributors like DO Supply, depending on condition, availability, and supplier, so check sites like eBay, Electrical.com, and DO Supply for current quotes. 

To get the best price, check multiple sources and be flexible with whether you need a brand-new unit or a surplus one, and remember to factor in shipping costs.