You stated unequivocally that "most transistors sold on Ebay are fake".? This is untrue and an unfair generalisation.
More correctly, SOME transistors sold on Ebay are fake. .
There is a simple reason for this.? Any supplier repeatedly selling known fake semiconductors would soon not be in business.
It is also very common for a failed repair by an untrained hobbiest to be blamed on faulty components. I repair this type of equipment regularly, its been a very good little earner.
I operate an electronic design and repair shop, concentrating mainly on the repair of legacy equipment. I have been reliant mostly on the same Ebay suppliers you mention,? to supply discontinued/obsolete semiconductors, and have twice in 30 years had occasion to question a supplied component/product. This suggests that the "fake" semiconductor problem is not as widespread as is liked to be believed., and I buy a large amount of random semis from random overseas suppliers.? Others in the industry also tell me similar, I have no reason to doubt them.? They also derive a large part of their repair revenue from well meant but? failed repairs? based on youtube videos or mods? performed by the hapless owner.....