Under Armour are selling a few T-Shirts at reduced prices on Amazon, this was the Large size in Red but also in Blue at this price. The prices vary with size/colour. The usual minimum spend of £20 for free shipping at Amazon or the cryptic 'wait until the last checkout page' before being shown shipping, oh Amazon!
These are around the £15-20 price each on other sites so worth buying a few to get the free postage.
I've not trawled all the UA items but a couple of other T-Shirts at a similar price are as follows: