How old is it? It might be worth something depending on age. However, like most old machinery whether or not it is deemed "antique" really depends on whether there's a collector's market for it. Unfortunately my experience with antiques is focussed more on musical instruments, furniture and jewellery. I'm not so good on gadgets.

As a guideline, new Necchis go for over £1000. It's a very pricey range of sewing machines.