That's true, but transistors (other than special mosfets etc) and 7805 type devices are so dirt cheap that why buy them from dodgy sources?
I think the "interesting" area for counterfeit parts, from the POV of the equipment builder, is expensive passives, like the RJ45 example I give above. It is very easy to make fakes of these, which may be way out of spec but will still function. And the incentive to buy fakes exists because if a part costs say $1 that is quite significant on a $30 (selling price) product, so a $0.30 fake is attractive.
The above video shows a lot of Yamaha parts, last made in (IIRC) 1995, and they would have been quite simple chips to countefeit and end up with something functional.
If you make non functional fakes (pretty much the only option for stuff like ARM processors, or even a Z80 which is quite a significant logic design project) then you will achieve just one hit on somebody and then you have to empty out that bank account, disappear, and start again.
A bigger problem is hacking the email accounts of chinese companies (seems to be very easy) and when you see a conversation where the context is a new order, and bank details, you fake an email with "updated" bank details. I've just lost $2k this way, and it is *very* hard to guard against. This is another topic