Amazon has the COWIN E7 ANC Bluetooth Headphones available right now for just $39.99, which is good for $30 off of its regular price, and that is a great price. Although you do need to use the promo code XZA7K8SD at checkout.
These headphones from COWIN E7 are perhaps the best pair you can buy for under $50, maybe even under $100. These offer up active noise cancellation, so you can zone out to your music and not hear what's going on around you. On top of that, they are super comfortable and lightweight, so you don't need to worry about them feeling heavy on your head. Thanks to the 40mm drivers in each ear, it provides some incredible sound, and some deep bass. Finally, the battery life is set at 30 hours, which is about the same amount you would get out of the Sony WH-1000X M2's which are nearly 10x the price.
This item is also eligible for Amazon Prime's free shipping. Which includes free two-day shipping, and pretty cheap next-day shipping if you need it here extra fast. If you are not an Amazon Prime member yet, you can sign up for a free trial of Amazon Prime by hitting the link below. You'll get 30 days free (if you're a student, you get 6 months), and then it's $99/year. Prime members do get a whole lot more than just free shipping though, so be sure to check out the full benefits.