I am a network engineer, I get a lot of 'logo' shirts.  There was always one type that just fit well and was really nice looking on me.  I never paid attention to the brand.  I was getting rid of older clothes recently and found my favorites were all labelled Port Authority and K420.  I'd rather not wear a logo when I am off of work so I googled them.  Found out not only can you buy them singly, but they are very low priced.

The quality of the shirt is amazing even compared to my $50-60 ones.  Plus the fit for me is perfect.