I’m considering using ThermalBuck on my DER renovation of an ’80’s vintage zone 5 ranch house and am wondering if the price I was given is reasonable, and what other options are worth considering. 

I like the idea of ThermalBuck a lot and would prefer installing it to constructing plywood boxes for each window opening.  However, at a quoted price of $51.34/8′ piece and a need for 54 pieces, the cost will exceed what I spent for either the exterior foam insulation on the house (unused, surplus 2.5″ polyiso sheets, John Manville ENRGY 3, from a building materials recycler) or the windows (facebook marketplace finds – primarily NOS Andersen windows and a few newer take-outs from remodels).  

So, is the price I have been quoted in line? And, are there time and cost effective solutions that will provide equivalent benefit to the ThermalBuck?