You have a problem putting value when dealing with such a scarce 'commodity'. Few verifiable transactions to give much indication of what it can bring at auction. Even less for what it can bring retail.
Several years ago I bumbled across an Antoninus Pius Sestertius being sold as unidentified by a French
ebay seller. I recognized the seated figure as Britannia and scooped it up for the price of an average bronze.
For larks I had listed it on
ebay for $350 assuming no one would be crazy enough to buy it. For a very long time nobody did ........
But one of your fellow Brits (Time Team alum) also bumbled into my listing and was happy to scoop it off me ! Sear actually lists these in the $1000 range !
If it floats your boat you might ask "Guy" if he has an opinion. He is a nice fellow and just might want it himself !
Carausius is his area of expertise