Well, it could have a value as acronym in the case someone need it, in that case the value could be above $100, but if no clue of someone will need it, the value is $1 - $10 range. for some domainer that want to buy it
Other alternative could be you ask the .com and .net owners to see if they are interested, the .net is a deloveped site. For this case I'd say $50 if they are interested or test a price you think accurate, but of course not sure they will be interested