I buy Fresh Clean Tees from their website. These are the best fitting t-shirts I have ever found, including many that were more expensive. A 5-pack of white tees is on sale for $80. They seem to last longer than others as well, but I did have one where the bottom seam came out. One out of about twenty.

I also pick up t-shirts at Target called Pair of Thieves. I have a few black ones and they seem good and long lasting. They have more of a soft synthetic feel.