I noticed that better quality shirts are often more resistant to staining because they have less saturation. I can sweat through a thin cheap t shirt. But a nicer one is usually thicker ( don't know if i'm using the right terms. maybe higher thread count?)They are caused by deodorants, but they are also caused by sweat, or a combination of both things. If you don't wear deodorants, you can still get those stains, right?
What washing technique do you use to get them out?
Have any of you invested in those expensive t-shirts that pretty much put a little pillow of pad underneath your armpit so that it doesn't stain through to the shirt?
I don't reside in India or Canada, so this is not a look that I would be comfortable with.
Also wearing undershirts