No saying you are wrong, just that I'm not convinced (yet).
Sorry but that's because you don't have an open mind here.
Well, all you have to do to become convinced is set a price target, e.g. $1000, or $2000, then compare what you can get prebuilt wise, to what you can build for that price.
But once again, you have to look at the long term to truly realize the value in your investment.
If you buy a Dell, odds are you will ONLY be able to upgrade the motherboard with another Dell OEM board because the case will be proprietary. That will greatly limit your options and surely, the replacement will not be at a bargain price. Same with the PSU.
These limitations also mean you cannot evolve your computer through many years of upgrades where if you build your own, or buy a custom built locally, surely you can upgrade the motherboard to just about ANY brand you want. You can move from Intel to AMD. You can keep your graphics card, or upgrade - YOUR CHOICE! All the while, keep the same PSU (if you purchased wisely at the beginning) and keep the same case.
Buying a PC from a big factory builder is almost as limiting as buying a laptop. You will have very limited upgrade options to carry you through more years of productive use. This means, if you build your own (or have your own custom built), you will get more years out it than you will any factory built PC.
Now if you are the type who wants all new every couple years, the by all means, by a Dell. But don't think for a second that you are spending you money efficiently.
Here is my thinking...
If an individual can put together a better computer than say Dell for the same price... then open a business and get rich... very rich.
Who said a "better" computer for the "same" price? Not me. IMO, that is NOT possible unless you just happen to stumble on some super deep discount sales - or buy used. This, again, is because Dell can go to ASUS and AMD and promise to buy 1,000,000 motherboards and CPUs over the next year and thus demand and get deep volume discounts. No way you, as an individual, or a small custom builder can get those prices buying just 1, 3 or even 10 units at a time.
And for sure, any Dell or HP you buy will have compromises here and there to (1) save Dell money and (2) meet the needs "
they" say you need.
So as I said above, it will cost a bit more initially - but
strategically, that is, over the long run (as in several years ahead), you will save money because you will have a tremendous amount of flexibility to upgrade here and there to keep the computer nearer the state-of-the-art and stretching out the total lifespan.
Can you get a nice Seasonic PSU with your Dell? One that will carry you through several upgrades? Nope.
Can you get the RAM of YOUR choice through Dell? Nope.
Can you have a Gigabyte board in your Dell if Dell only offers an OEM Foxconn? Nope. What if you'd rather have an ASUS. Forget about it. Custom built? No problem. What model would like?
If Dell offers a 1Tb WD SATA SSD can you get a 3 TB Crucial M.2 instead? Probably not.
Flexibility may be an "intangible" (can't put a $ value on it) asset but isn't it worth something to you? It sure is to me. Its worth a lot, actually. So is a longer life expectancy that I can surely expect out of my case and PSU too, as well as my graphics solution, keyboard and mouse.
There really is no comparison, or doubts about. A properly researched self/custom built PC will save you many $$$€€€£££
over the long run. Period.