I wear suits at work fairly often; it depends on the client and if I'm interacting externally often in a given week (month). I like wearing a suit: I have an enhanced sense of professionalism and self-confidence when I'm dressed to the nines.

I'm not a developer or in "tech" in the pure sense, and I know this depends on the "culture", but I'm also on the East Coast and a bunch of our devs have Bow Tie Tuesday and really get into it. May be a geographic thing as well: I'm as like as not to wear dark jeans, nice shoes, a button-down, and a blazer on weekends.

And it isn't cheap. If you shop around, you can find a reasonable suit for under $500, which is still a fair amount of t-shirts and hoodies. However, the key to dress clothes more so than quality is fit—you should have all your suits tailored to fit you, and that's another $100 or so between jacket, pants, etc.