Ask the MB: Sheer Dress Shirts
A: Without boring the absolute bejesus out of regular readers with a thread count discussion, the sheerness of a fabric is a combination of thread count, quality of the yarn, and weave. A fine-yarn shirt can have a high thread count (high density), cost $250, and still be sheer. You can also buy a low thread count, non see-through shirt at Burlington Coat Factory for $19.99 .
If you are opposed to wearing a shirt under your dress shirt (we strongly agree with that stance) and are hung up on sheerness, then focus on the weave rather than the thread count. Look for twill weaves or oxford weaves (but not at Burlington Coat Factory).