I was experimenting with Amazon's implementation of this recently (having had to honor lame MAP pricing when I did internet retail websites), and it's interesti

I was experimenting with Amazon's implementation of this recently (having had to honor lame MAP pricing when I did internet retail websites), and it's interesting that it's merely behind a click, it doesn't actually add it to the cart and then have you remove it. The wording is just that it's been added and is in your cart.