Of course they're allowed. When you run a business, you set the price of the items you sell.
Not if you are buying direct from say ASUS. They have MAP pricing.
LMFAO do you even know what MAP pricing is? It's the MINIMUM that you can advertise the price for to protect people from backdooring and driving prices down. They don't give a flying fuck if you sell it for $5,000, but if you ADVERTISE IT below what they tell you is allowed, they pull your seller status.
And that's why you see sites saying "Add to cart to see price" - because it's a way around MAP.
Do you know what MAP is? It's the price you HAVE to sell at dumbass. Yes, you can sell it less by using "add it to your cart", but they also can pull those products from your store if they wanted to.