You do realize that the prices in the store right now are already the maximum the stores can charge, do you not?

The market doesn’t see the price hike. You pay $100 today, before I hike the prices. I hike the prices to $111.11, but my shelf labels show you the “discounted” price of $100. You keep paying the $100 price that the market currently bears.

And why can’t the elderly or disabled use self-checkout?

That point was completely irrelevant. If someone can’t use the self checkout, ADA compliance requires accommodation, and the business can’t charge them extra. They get the same discounted price as the self-checkout. So, they put a handicap placard on the cashier stand, train the cashier not to ask any questions about disabilities, and give the same “discount” to anyone who uses the register.