Woot offers Amazon Essentials Men Crew Undershirts 6 Pack for $9.99 free shipping with Prime. 

Product Description:
We listen to customer feedback and fine-tune every detail to ensure our clothes are more comfortable, higher quality, and longer lasting—at affordable prices for the whole family.
 

• SLIM FIT: Slim fit through the shoulders, sleeves, chest, and waist
• COTTON JERSEY: Soft, smooth cotton blend. This lightweight natural fabric feels soft against your skin, while the added spandex offers a flexible fit that moves with you
• CREWNECK UNDERSHIRT: A casual undershirt design, offering both comfort and functionality for everyday wear
• DETAILS: Designed with short-sleeves and a straight hem which are finished with super soft flexible stitching. The crew neck is banded for extra durability and has a printed label at the back neck
• GARMENT LENGTH: 29" from side neck on US size Medium