I think asking to get a payback on a certain card for 6-8 months is not possible during such time that we are in.We are still in a crypto winter and this is the best time to collect coins,you either mine them,which is what I do or you invest in them by buying them.Electricity I think is a key factor for people running more than 3-4 rigs while for people running only one rig even if the electricity is a bit high it is still affordable in the sense that people can even pay a bit of loss by waiting for the next crypto craze which can bring insane profits if done right.

I am using a Mac mini as I type.

I have 3 in the house. They allow me to run core wallets safely. They are more secure than windows in general. less secure that linux. But you can run linux on them.

I'm from Vietnam so local reviews cover something that is very obscure and questionable Chinese products that you won't see anywhere. A bunch of dudes found something very cheap but questionable quality/price, a dude with technical background brought it first and broke it down, testing to see what was inside them and telling the other if it was worth the price/performance for social creed. We've some really old bb forums that took root from overclocking and PC hardware since 2006. Also, some VGA is at the end of product life so I doubt if you could find a truly new analogue for that VGAs (1060, 580,...)

You're right. Just like we should not download the products of those who are not ready to communicate with the audience, and as I see it here, it is "VERY LARGE".
As I said, conclusions have been drawn, the review has been compiled.

IF electricity is inexpensive. I know there are very few places where electricity is not expensive. Now what if OP is not from such an area, what advice do you give him?

I was only giving him an alternative and it's surely not bad.

Right now I am in Albania from some years,relocated here for work and it looks like will be staying some others too as my child is growing up here.Yes whenever possible I have bought cards through Ebay but there is a lot of corruption in the postal office here and one time I have ordered a good one,and received one that the fans were not working,probably some guy at the customs or post office did it as the seller in Ebay is someone I have always bought and his feedback speaks for him.This happens rarely but it is enough to stop me from buying abroad.

For Powercolor I am very happy with the performance of the Rx 6800 XT as I have three of them and they all run super cool even in the middle of the summer.

Do they really recycle the old memory chips? If you take a GPU it usually has about 8 memory chips. And its very easy to remove these chips if you have the right equipment. Heat it up for a minute or two and remove it with a suction pen. The pain will come right after.

Its very difficult and time consuming to take off the old solder and then you need to carefully apply the balls on the solder joint, you use a stencil to do this. Again this is doable however doing 8 chips will take 30-60 minutes depending on skill level. If this was reballing some GPU chip for a product worth $500 it would be worth it, but to go thru this hassle of reusing the memory chips just sounds crazy.

Recycling old memory chips has been a trade for China's brands for a while. Not just GPU memory but also others like RAM, and NAND flash memory,... You may not know, but some China NVMe SSD also uses shitty or low-yield NAND or even recycled NAND from used SSDs. The same for some questionable Chinese RAM brands like Kingfast or Kingspec (copycat of Kingston name).
Dead VGA cards with untouched VRAM could still fetch a good price even if it not working or are completely dead (ten bucks for RX 470/570 model with 8GB last I check). To be honest, it was very eco to make use of everything even the old and busted memory of all kinds. Still, advertising it as a brand-new product is dishonest. My advice: don't take anything from China's market at the face value, check reviews from many other customers or broke-down, disassemble reviews like OP mentioned.

Unfortunately where I am there are only high end cards in the used marked also,there is only Rx 6700,6800,6900 and very few Rx 5700 Xt-s here,we usually only have Sapphire or Powercolor brands so Sapphire which I agree is the best brands for AMD cards is widely used here.The prices though are much higher than that,some people here at 150 dollars are selling Rx 580 8 GB cards so here prices do not drop as much as in other parts of the world,people are attached to their things and want the highest possible monetary value for them even when the time of such device has passed.

A good thing though,Nvidia guys usually sell their cards a bit cheaper and that is why I have mostly Nvidias now in my rig,I have shut down the AMD devices.

Mining is a long term venture mate, if you are planning to make profits, maybe 3 to 5 years, that is if you don't even sell your mined coins at low price. Even those chaps who mined 50 Bitcoins at ago back in the day realized great profits at HODLing the mined coins after some time.

Now I shouldn't be the kind of person to tell you this, but If I were you with $3,000, I would just buy a coin and wait it out in a couple of years. There are very high chances that the $3,000 turns into $6,000 or more. Lately, that's very hard to achieve with mining in such a short span of time.

Bitcoin mining is the process of using computer power to solve complex mathematical problems in order to verify transactions on the Bitcoin network.

Miners are rewarded for their efforts with newly minted bitcoins and transaction fees.

The difficulty of the mathematical problems adjusts dynamically to ensure that the average time between mined blocks stays at about 10 minutes. As more miners join the network, the difficulty increases to maintain this average time.
This process helps to ensure the security and integrity of the Bitcoin network. The energy consumption of the bitcoin network is very high.