We did without for a long time, but it seems that more and more retailers make use of the barcodes, and according to our distributor, there are a significant number of retailers that will not accept a product without a barcode.

The cost for having your own barcodes is steep - GS1 charges about $750 the first year, half that I think in subsequent years - but as you said, it does identify the product as yours specifically, which will have some value if, for example, the product is wildly successful and you decide you do want to distribute it.

The other option is, you can get the barcode allocation from GS1, so you have a permanent barcode for the product that's yours, but if you already have covers printed, you can make stickers with your own individual barcode for that product and just sticker the existing covers until you run out and have to print more.

If you're sure you'll never wholesale the product, I'd say go without. If there's a reasonable possibility that a number of retailers will want it, I'd say put a barcode on the product, either your own or one you license from someone else.