Before I continue, below are links showing hundreds of examples of forged Mickey Mantle baseballs, photos, etc. found on Ebay (the most dangerous place to buy autographs if you're a casual collector or impulse buyer).

https://live.autographmagazine.com/forum/topics/ebay-mantle-dimaggi...

https://live.autographmagazine.com/forum/topics/examples-of-mickey-...

https://live.autographmagazine.com/forum/topics/most-common-mantle-...

So when does a Mickey Mantle autographed hat/cap sell for $88.77?

When it's an obvious forgery.

Why did it sell for only $88.77?

Because knowledgeable autograph collectors didn't give crap like this a second look.

This is your typical and mass-produced Mantle forgery-style that was so prevalent in the 1990's. 

This one was sold by Ebay seller Blues0711.

I hope the person that purchased this submits it to Beckett or JSA.

This crap sells because Ebay is so heavily-populated with delusional autograph collectors and impulse buyers, and Ebay does not care--They've made huge amounts of money from the sales of forgeries from the past twenty years.

https://www.ebay.com/itm/Mickey-Mantle-Autographed-Yankee-Cap-with-...

Ebay seller Blues0711 also sold the below forged Derek Jeter cap that sold for a whopping $150.00.

Look at this crap.

https://www.ebay.com/itm/DEREK-JETER-Yankees-AUTOGRAPHED-Signed-Cap...

Worthless COA.