You may be missing the "and be added to the final price" bit, or interpreting it differently than it may have been intended.

In European countries with VAT, the price on the item / shelf tag / whatever includes the VAT. You don't need to remember what jurisdiction you're in and thus what percentage of sales tax you need to add on to the displayed price to know how much you'll be asked to pay when you check out. If the tag says 12 euro, 12 euro is exactly what you're paying at the register.

Sure, in the US, your receipt will tell you how much sales tax you paid. But that is information you're not given until the point of checkout. Additionally you may not have the explicit tax amount presented to you til you receive that post-sale receipt, you may have to do your own subtraction of the listed price(s) from the total price to determine how much tax you're paying before you commit to the purchase.

I think he means the display price. When you buy something for $100 and it ends up being $110 on checkout, the taxes are obfuscated on the display price.