"It says $80 online" "Here, let's pull it up on the website, $100, you must have been mistaken" Head home, nope, $80.
They got caught - or provably so - when mobile data became better. "Weird, if I turn store wifi off and hit refresh by 3G the price magically goes down".
That ended up in a lawsuit, and no doubt some gift certificates via class action.
"Target updated its smartphone app Wednesday night after a Minneapolis TV station reported that some prices displayed on the app increased whenever users approached a store. In one case, a product's price increased by almost $150." ...
https://www.cbsnews.com/news/target-app-price-switch-target-...
What generally happens is: (1) associate is dispatched to pick an online order, listed by SKU and bring it up front, (2) they arrive at the bay and start looking around for a match, (3) while they are supposed to verify down to the SKU level, sometimes they say "DeWalt 20V circular saw" = "DeWalt 20V circular saw", grab it, and move on, (4) repeat for the next order.
That's assuming there's stock in the store. In the event it's Ship-to-Store, you add the additional touch of warehouse getting it right. Although in my experience that rarely goes wrong (because automatic verification, etc as things go out).
I always do a SKU / item check if there's anything that might be a problem. In my personal experience, it happens ~1:50 orders (usually with easily confusable substitutions).
I was recently at Lowes, I had found a Saw Horse online at their website for $80 off, and tried to price match it to themselves but when the cashier looked it up it came back the store's price (even though I still had the page open on my phone, and at my home computer at home).
Then got treated like I was the one trying to pull a scam, rather than them discontinuing a sale mid-way through a work day, and me being caught by it.