It takes 60 HOURS and thousands of dollars to make every single custom suit for Conor McGregor ... and the guy has DOZENS of 'em ... so says his personal custom suit guy (yeah, he's got one).

We spoke to the UFC guy's longtime wardrobe guru David Heil -- CEO of David August clothing -- who says McGregor is an animal when it comes to fashion.

Here's the math -- each custom suit ranges from $4,000 to $10,000 ... and Conor orders 8 to 10 outfits every single time he goes out on a media tour.

"We also have 2 or 3 extra outfits on hand in case anything happens to the outfits he’s supposed to wear for an event."

Translation -- money is no object when it comes to Conor's look.

And Heil says he's a full-service outfitter -- "From the suits down to the bow ties to the cuff links, he’s wearing David August."

"Every outfit I make for him takes 60 hours. He likes to wear his suits high and tight and really tailored, and his size changes all the time depending on his fights. So we’re always measuring him to make sure it fits exactly how he wants it."

"He’s such a style guy ... he’s always been that way since the day I met him. He takes everything and makes it his own. It takes a guy with the right mind to pull off these extreme looks, and he does."