1977 topps Walter Payton
 

So there has been some recent sales of this card that have went very high. I have noticed that there are 3 card uncut sheets all over eBay .
Is it plausible to buy them and cut a 9 or 10 out of it?
Where did all these uncut sheets even come from ?

PSA and SGC won't grade sheet-cut cards, but Beckett will

Like the gentlemen above me stated, only Beckett will grade "sheet cut" cards. I've seen a ton of uncut sheets in my collecting days. I suppose if you could get a sheet at a good price, you could get whatever card you wanted cut out and sent it off to Beckett, hoping to land a 9.5. I've never tried it as I'm not a "flipper" nor would I want a sheet cut card in my collection. :)

I will admit though, recently I saw a 1980-81 Topps uncut sheet with Bird/Magic/Erving rookie and it was intriguing to say the least.

I would say yes, I think the Honus Wagner is cut from a sheet. I've seen other high grade cards that looked trimmed to me. Once its graded, it becomes a matter of opinion.

I don't know that BGS would be the only grader for sheet cut cards.
The magic and bird rc sounds very intriguing lol. But how would anybody
Go about cutting it perfectly?

Run a PSA pop report on 1985 topps minis and I can show you over 600 number graded sheet cuts right there.