12k monthly searches isnt great, most other extensions have been regged which could be seen as positive. Its .co, which, im coming to like more and more. Overall i think less than $100 undeveloped.
A blog on sponges (there is more to sponges than just what you wash your car with) and some advertising.. maybe you could make a few dollars a month revenue.
Its not the most exciting domain word or name.
Though to a company that makes sponges for wholesale.. who could tell the value. its a nice one to sit on for a while.