If you fail to ship anything, that's an open and close case of fraud. If you ship anything, especially if it's at least superficially similar, you can argue it was a good-faith mistake, just a case of failed due diligence.
Also, there's this interesting exchange I had with an eBay seller a couple of years ago. I purchased a bunch of NiMH batteries. Because I test every component I buy even for my hobby projects, I immediately noticed that they were 1/10th the capacity that they should have been, and were marked as.
I contacted the seller to return them and get a refund. They told me "honest mistake" and then began a negotiation. "How large of a refund would you accept?"
Since the batteries were useless to me, I said "100%". In the end, I did get a complete refund and didn't need to return the batteries.
Fun thought: since eBay often rules in favor of buyers, it would be fun if someone would 'abuse' this: buy a good # of often-faked parts from all sellers that offer them, test extensively, and open disputes for any fakes received. That should (in theory) cause a good deal of $ losses for any seller that sold fakes.
Maybe repeat regularly, and it might remove some fakes from the market?
Back when everyone was making Windows 8 tablets with a quad-core Atom and a $350 price tag, I ordered one of theirs. It got good reviews in the Maximum PC comparo of the time, and it was available with a then-cavernous 64Gb of flash.
In week 1 the Wi-fi wouldn't keep connection. By week 2 it had fully bricked. I initiated the RMA process, and the chat monkey asked "If we refund you $50, would you keep the device?"
I ended up getting the Asus version which had a nifty little clip-on keyboard, and it at least lasted the warranty term before the touchscreen cracked.
I did end up getting a partial refund for about the price of a replacement OLED screen.
If you're going to commit fraud, at least be honest about it.
Second, being honest about commiting fraud is counter-productive. Comercial fraud, even though illegal, is still a commercial enterprise at its core and its goal is the same as of any other comercial enterprise: to bring in profit, the more the better. Fraud is not about sending a message on ethics, or showing off someone's character, or helping the marks to keep their money, it's about getting as much money as possible at little cost as possible (with the costs of dealing with legal persecution accounted).