Due to the abundance of sewing machines antique, vintage and otherwise.... the value is not that great.
There are a few exceptions if in mint to near mint condition:
- The Singer Feather Weight has some value especially if you have the original case and attachments
- The "Red Eye" (see below photo) I have seen these sell for over $1,000 on eBay but they were in perfect condition and working, there was little if any wear to the decal and they were stunning.
Remember... condition is key and you must be able to find a buyer. Any item is only worth what someone is worth paying for it.
You can use the pages listed under the sewing machine resources to view more information about these vintage and antique sewing machines.