Not sure where you are based but do a search of your local area for Commercial espresso service/sales companies. Your machine is a BFC Diadema model 2GV EL and a commercial espresso service/sales company will have a fair idea what it is worth.
PS. If there is nothing wrong with the machine, why not get it serviced and continue using it. This maybe more practical especially if it is not worth much. It maybe a bit too big for your new staffing levels/office size but I bet it makes a great coffee. (14/02)