If you are buying a material amount of gear, and have your own internal accounting/finance people to establish proper etiquette in purchasing, Dell will never "lose" based on price. As customers, you can say what you're willing to spend on a solution, if you understand the BOMs and all the details and "the business rules" then Dell can be a good enough partner.
We operated a hundred petabyte sized warehouse, and did it at the fraction of the cost of cloud services even factoring in engineers, networking, power and redundancy and DR.
I've ordered from Dell and Supermicro (and others, but not in volume or often enough to have much data) for a couple decades now.
Supermicro you consistently get a good/best price. It's already pretty low, so going from a 10 unit order to 1,000 unit order gives you some discount but nothing crazy most of the time.
Dell it's basically based on phase of the moon. I typically tried to time my smaller purchases to coincide with end of quarter. Wait for my rep to call me and ask if I had anything for him. If my little 6 unit order helped them or their boss hit whatever target you could get amazing deals. Stuff where they wouldn't budge 2 months earlier could be had at below supermicro pricing. More than a few times they would give such ridiculous pricing that I considered ordering way more than I needed to part out the components on eBay and just recycle the sheet metal and motherboard.
Other times/years (and different reps too!) would give a budgetary quote for a build and say they'd match a Supermicro quote which was nice, but took extra work and never feels great when you know you're using a vendor just to get pricing down with the one you actually want to go with.
I just hate dealing with that junk, so I tended to prefer Supermicro to reliably get decent pricing when I needed the gear vs. having a whole strategy around order timing.
Then you get into stuff like hard drives/SSD and that was a whole thing w/ Dell for quite some time. These days they are competitive but they were not always.
