Usually in stores that have kind of salesmen involved when you purchase a lot of stuff they are more eager to give you a discount as for them they make more money. So often they wouldn’t want to lose say a $300 commission over an item that costs the company only about $20 per se. What I have seen done many times to increase these deals is to try and shop with your friends and family at the same time assuming you all need certain types of purchases.
An example could be that you all need to buy some kind of furniture and so you need to go to the furniture store. If it’s something like you need to buy a bed while the other party needs to buy a sofa, simply making it seem as if this is one big package purchase will often garner some extra deals. A recent example I did see was that one person was buying a new mattress and the other was purchasing a dresser. Believe it or not, they were able to get a free bed frame as a result. Pretty simple way to save some money.