Sears offers the Monster iSport Strive In-Ear Headphones, model no. 128946, for $49.99. Plus, Shop Your Way Rewards members earn around $21 in SYWR points. (Not a member? It's free to join.) Assuming you'll use the credit, that's the lowest total price we could find by $21. They feature an in-line microphone, sweat-proof design, and SportClip.
Of note, Shop Your Way Rewards members may be eligible for additional credits and discounts.