I had an odd experience at a large online retailer (call them AtoZ). I'll happily edit this to include the actual name if that's permitted here.
I selected an item that was indicated as sold and shipped by AtoZ, at the listed price of $12.50. I added a quantity of 5 to the cart.
At checkout the price was shown as $15 each, from a third party seller. I placed the order anyway, figuring I could resolve the difference through customer service.
It took a second-level agent to explain what happened. Apparently this is how their algorithm works. If I'd bought just one, I'd have gotten the advertised price, but buying five changed the deal (with no notice) and brought in a third party who was free to choose a different price.
The agent said they've had many, many complaints about this, but it wasn't anything he could change. He suggested I place five separate orders, spacing them out over an hour or so because the algorithm would 'forget' each order after some time.
That mostly worked but it cost them free shipping on five $12 orders, plus a half-hour of phone support, for a likely overall loss.
So, was their original price increase a bait and switch? Would I have had any legal recourse?