Lands' End offers its Lands' End Women's Plus Size Long Sleeve Relaxed Cotton Mock Turtleneck
in six colors (Deep Lilac pictured) for $6.99
for shipping. That's $17 off and the lowest total price we could find. It comes in sizes 1X to 3X, although not in all size/color combinations.
Note that it's also available in limited regular and petite sizes for $5.99.