Do supermarkets/grocery stores test customers by doing weird things with pricing?

I've seen that numerous times. One major chain here has a lot of 5/$10 or 10/$8 deals. Many think you have to buy the full amount to get the lower price. I even asked an employee and she though you had to do so. They are always testing us. I could give you many more examples. I check everything before I buy.

In chain-stores, prices are set by corporate - not at store level.  Prices are based on things like product availability, manufacture discounts or promotions, or time of year (seasonal; promotions).  Some pricing is set by computers, and 90% of pricing is done months in advance so as to coincide with certain events, seasons or expectations and be printed in sales fliers.Most pricing has to do with what manufactures charge the stores for their product.  The more a store buys, the cheaper they can get it.  Many chain stores have "buyers" - people whose job it is to purchase merchandise at the cheapest possible price from wherever they can get it.

Markup (the difference between what the store paid for an item and what it resold it for) plays a big part in pricing.  Certain items have a high makeups (sometimes over 100%), therefore a store can put these items on sale more (and perhaps for longer times) and still make a good profit.  

When a new item comes to market, most are discounted by the manufacturer to help generate sales.  Although stores can buy these items for less, not all of them pass this discount along to their customers (especially non-chain stores).

Then there's what's called "overstock".  This can be localized to 1 or 2 stores.  if an orderer has "fat fingers" when ordering, 3 platelets of a product can accidentally turn into 333 pallets.  While some warehouses will take back the mistake (at a cost to the store), some wont.  Some store may try to put these items on a quick-sale to get rid of them (back-rooms space is very limited in stores),  However, if it's something they think they can sell off at regular price (say 333 pallets of bottled water in July), they'll just make huge displays of them around the store (inside and out).

Then there are schematics (the map which shows store personal where to place each product).  Schematics are also usually set by corporate.  There's an entire science behind product placement and customer purchases.    Unfortunately (according to corporate), all stores aren't built/located equally.  Some stores are bigger or smaller than others or have a different demographic.  Therefore they all don't carry the exact same product.  For example, a store that has a high hispanic population will sell more hispanic items than an area with a low hispanic population.  If a store cant sell an item, they lose money so they want to carry items they know they can move.

Of course, the People who do pricing at store level are human, meaning they aren't perfect.  Sometimes they make mistakes (you try changing prices on over 50,000 items across an entire store in one night).

All this happens behind the scenes, meaning customers don't see it.  However, what they may see is strange shelpf prices.  Yes, stores have "tricks" they use to boost sales (buy one get one free, 10/$10, and such).  And yes, customers need to be a bit price savvy when they shop (go by price per unit NOT sale price).  However, we  in this country are spoiled by the amounts of items we have available to purchase at our local stores and the ease we have of purchasing these items.