I call such tactics "Spray and Pray", like the military guys say about machine gunning.
Better to have and not need, than need and not have. Old common sense saying that nobody seems to heed.
It cost you NOTHING to take it back next time you're in there ANYWAY for something else. It cost a LOT for you to have to stop a job and make a run for more whatever.
I was going to make that customer appointment, but instead I've got to run to Lowes for two sheets of OSB because I've got 10 roofers with their thumbs in rectus - so I'm going to be late.
OR
I just got finished selling another roof when my roofers called and said that I've got two sheets of OSB to bring back at my convenience.
Which is the smarter choice?
I'm going to goober gauge at the job for two hours contemplating exactly which parts I'm going to need so I don't "waste" any money buying returnable materials. Then I'm going to go to the store and buy only what I think I need - maybe goober gauge at the store for another two hours. When I get back to the job and start actually DOING something, I'm going to find out that I've got to go back for a pvc fitting. Simple job is gonna take two days!
OR
I'm going to buy $100 worth of **** I don't need just in case, then return $75 of it at my convenience. Store trip and job combined - 2 hours, maybe 3 if I'm being slow ...
It bends my mind how many times I see the wrong choice made in these scenarios.
I often take a shotgun approach to a project, especially when it involves PCV pipe and fittings. I'm likely to fill a basket with anything and everything I think I might possibly need and then return 75% of it (or more) at my convenience. I don't need a receipt as they can link the purchase to my credit card. The cashier doesn't bat an eye.