Reason it's an expensive fake, is someone paid alot more than it's worth, to buy it, then someone else spent it.

Here's how it's made. The tails side of a real coin is carefully machined out, up to the edge of the rim. Then the heads from a second coin, is carefull made the size of the removed portion, and inserted. There's a very small line, along the inside edge, next to the rim, where you can see the new heads has been inserted.

Why I'm about 100% sure it's not real...

The mint uses two different mounting systems for coins two sides. They can't put a heads, into the tails side of the press by accident and visa versa.

I've seen a number of these that are quarters. I suspect that people who had them, spent the trick coin by accident. At least with a half, or an Ike, you know it's some change that's not mixed in with the rest, by accident.

Keep it and win bets, always pick heads of course.

Not a mint error.