'No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.'
In this case, local hidden variables refer to what you describe as it being in a single state and us just not knowing. Without faster-than-light information transfer (which we cannot have if causality is to hold within relativity), it is not possible that 'the system is in a state and we just don't know it. '. Quoting wikipedia,
In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that a theory could not be Lorentz invariant.
This has been shown experimentally using Bell's equations and this work got him nominated for a Nobel prize but died before it was awarded that year.
I think the real problem here is that Walmart are trying to overprice people and then console them with the offer that if they can bring in a cheaper price they will honor it. The real solution would be Walmart not overpricing, but clearly they are not prepared to do that so they offer these deals.
These deals trick consumers into thinking that they will obviously get the best deal there as why else would the shop offer this deal. The cashier does not necessarily know how much these items are worth and it is clearly not their fault. It is a large company trying to extort as much money as possible from the people who do not bother. If they are not willing to put in price checks with other shops and keep wanting to overcharge normal customers, then this is the way they must do business.