Lids takes up to 75% off a selection of NCAA, NFL, NBA, MLB, NHL, and other clearance caps, with prices starting at $5. (Select styles may have an even larger discount.) Shipping adds $4.99, but orders of $50 or more bag free shipping. A couple of best bets, each with $4.99 for shipping:
New Era Dallas Cowboys 2016 Official NFL Sideline 39THIRTY Cap for $20 (low by $10)
New Era Chicago Cubs MLB 2016 World Series Champ Patch Authentic Collection 59FIFTY Cap for $25 (pictured, low by $8)
There's a less expensive way, and then there's the way that works for you. The two may not be the same.