They look like bankers on lunch break but do some hillbilly engineering in their dirty garage, so why are the wearing shirt and tie? It took me right out of the movie. Anyone in their position would have gotten into more comfy clothing first.
Took me riiiight out of the movie...
This was mentioned in Shane Carruth's commentary on the DVD. He said he dressed Abe and Aaron similarly to each other in every scene. In almost every shot when one has a tie, the other does, when one has a sweater, the other does. They are two sides of the same person, psychologically-speaking.
In addition, having all Abes and Aarons (1, 2, 3+) dressed identically assisted in the mystery.
Last, this is a $7000 indie project and rewearing the same $30 shirt from Wallmart was good enough for "engineer's off-duty uniform".