Found a DELL XPS8910 with a RX 560 at Ebay: NEW Dell XPS 8910 Mid-Tower NICELY LOADED Quad i7-6700 RX 560 1Tb 16Gb Win10 Pro 641275615782 | eBay . The description mentions a Customized Dell computer.
When I go to DELL website and Input DELL XPS 8910 the only models that pop up are XPS 8930 models. Which indicates that Dell doesn't sell that particular model anymore (XPS 8910).
When you google XPS 8910 and go to DELL.com it is showing the model from 2016 with the latest GTX 9xx series card. It is possible that Dell replaced the AMD R9 370 or Nvidia Card with a RX 560D to help sell it to Costco. That is just my opinion on how Costco ended up selling a Computer model that seems to have been customized for sale by Dell.
Like the link I posted > https://www.amazon.com/Dell-8910-Special-Silver-Desktop/dp/B0785SDHBF/ref=sr_1_3?ie=UTF8&qid=1523637... Maybe it's the Silver Special...either way...I would return the computers to Cosco. There is enough facts to show that the poster did not get the version he thought he bought....why would any computer manufacturer have identical named computers with wildly different components. he was shipped the wrong computer...It would be helpful to see Cosco's advertisement for it.
I can understand your frustrations as I have fallen into the "OEM vs Retail" specs' trap myself a long time ago when I purchased my first desktop from Gateway Computers. All computer manufacturers like Dell, Lenovo, HP, etc', use proprietary components (parts manufactured to their specifications) and system BIOS. So there are a limited amount of customizations and upgrade choices available. They would prefer that you just buy a new computer from them.
Here is an old write up that that I found, that is still true for today and may help you in the future. See the part under "Customization".
I hope this is of some help...
The GPU-Z image indicates he has a RX 560 card installed. It is possible Dell installed the Cutdown version of the RX 560 which is the RX 560D as mentioned by the OPS to cut costs on the computer system. So does Radeon Settings image also indicate a RX 560.
I saw your link and googled it to Dell.com. It is a 2016 model. These Desktops can be customized by the buyer. They can add or update many of the components from the base model. So he received what he bought. Looks like Costco ordered from Dell a customized version from the Base version. Your link proves that and the link from Ebay proves that.
I agree, It would be helpful to see how Costco advertised the computers. If Costco purchased from DELL using the RX 560D they didn't advertise falsely when they said it had, according to the OPS, a "REAL AMD RX 560" Card. The card is a REAL RX 560 just a slower version.
What is the OPS going to say to Costco, You lied to me. That is not the regular RX 560 but a slower version? Costco is going to say they advertised a RX 560 just not what version.
The OPS already mentioned that Costco would accept a return (Costco will accept these 3 computers back as returns (beyond 90 days) but wants to keep it due to "the deal was unbeatable" .
That is why the deal was unbeatable because the computer had installed a cheaper slower version of the RX 560. If the computer had to regular version the price probably would have been much higher.
"There is enough facts to show that the poster did not get the version he thought he bought." where does it show that the OPS didn't get a RX 560 or a totally different model?
He paid for a computer with a RX 560 and that is what he received. If Costco advertisement just mentions RX 560 they didn't lie. Costco just failed to mention which Variant of the RX 560 was installed. It looks like Unethical advertising not to mention the Variant RX 560 model but not illegal.
Now if Costco advertised a computer with a RX 560 and instead got a very cheap and slower RX model with a different model number, Than the OPS has reason to believe he got scammed.
It is a very good price for a startup computer. The computer case is large enough to add many other components to customize it the way you want in the future.