I saw something once that 90% of baseball autographed items are fake.
I might buy a guitar autographed by Pete Townshend. They say it is certified but I don’t know what that means.
I’d imagine the percentage of fake items on ebay is about the same across the board regardless of what the specific item is. I’d pass.
“Certified” means that it has been submitted to an authentication service that has issued a certificate giving their opinion as to its legitimacy.
The key question is: Certified by whom? Find out which company/dealer/service did the authentication, and then research whether that service is considered reliable by others in the industry.
In college my econ professor used this exact example to show how value and markets work. But the real answer to you is an economic one: How much more are you willing to spend to guarantee authenticity? vs. having a non-zero probability of it maybe being a true signature? But then you also need to think about what you want to do with the item/instrument- if playing it vs. putting it on a shelf to increase in value. They have different thresholds. So one should pay as much as 1. they think they can get back in the future upon liquidation or 2. the happiness the item brings. If #1 is the goal, you are defeated already because you were the highest bidder! (at least until inflation) So just go for #2, and only investigate the authenticity if you NEED to know.
Seconded. And remember that even if the company is legit the certificate itself could be a counterfeit. I know how many coins and currency items I’ve seen slabbed with a fake slab; I do not want to even think about how easy it would be to rig a faked certificate or even background for something like a guitar.
I can print out and fill in a certificate of authenticity that you would have no way of knowing wasn’t bogus. I can even print out an embosser on my 3D printer to authenticate my certificate of authenticity.