You can invest in such devices if you expect a problem in the supply chains, have experience and trust to be able to sell them at the right time, but in general electronic devices are not an investment because their value is declining over time due to the presence of better and more advanced devices always, in addition to the increasing difficulty of Bitcoin mining.
So unless you have experience, a good plan and know what you are doing, buying a Hardware hoping to make a profit is a wrong strategy.
Yeah you really need to know what you are doing if you think you can buy 10,000 in mining gear and flip it for 20,000 in six months.
BTW July 2020 Ebay was selling bitmain L3+ miners with a psu for about 100 USD
Same gear is now over 1000 USD
I would argue mining gear is very inflated do not buy, but If you purchased in Jan to June 2021 you likely did okay.
So if you buy today will a piece of gear be 2x in a year .
I have zero idea.