It annoys me that Draft2Digital insists that they have to add the 90000 supplementary barcode. It's simply never printed on books in the markets I want D2D for. I have hardly any books with even the UK price in the Barcode since the book price setting by publishers was made illegal in UK and Ireland. Irish shops had to stick a price sticker or blank that as even before Irish pound broke with Sterling and became Punt, the publisher set prices were higher in Ireland.
Is the supplementary 90000 barcode on all books in the USA if there is no price code?
Why does Walmart need a different code? Regular retail products have an EAN/UPC barcode. These uniquely identify the item (Heinz regular size baked beans or whatever) and the current ISBN is simply 100% compatible where the 1st 3 digits indicate a book (Bookland country code). Neither true EAN/UPC or ISBN encodes the price, only a product or title.
The supermarkets and bookshops here simply use that regular ISBN the same way as any EAN/UPC on any product they sell. The shelf price label (either paper or eink) usually also has that code in non-book part of supermarket, and by law the shelf or sticker price takes precedence if the POS price is higher. Books are usually priced per shelf or a price sticker (two stickers if a UK chain in Ireland) for the customer, but the basic ISBN without price code is used at POS to lookup price. Publisher pricing of books is now illegal. Wholesale setting retail price was common for nearly everything in still in 1950, The UK Co-op even had its own radio brand as they could not discount. Gradually made illegal and both medicines and books were the last to go in UK & Ireland.
See
https://en.wikipedia.org/wiki/Resale_price_maintenance
It's illegal in entire EU and UK now for all products.