I have the opposite problem. I work at a place where everyone dresses below the standard (that is, the standard of any place that isn't a podunk middle-of-nowhere town like this). I get a lot of guff from my coworkers for dressing too nicely. Apparently, they think I dress nicely because I want to look fancy and better than them. Really, it's just because I have all these professional clothes and don't want to waste them, plus my wife likes me to dress well and a happy wife = profit.
So, I commiserate with you from the opposite end of the spectrum.
The problem, it seems, is just that people just don't deal well when you dress differently from them. I wish I were in a workplace where people were encouraged to dress nicely. I don't feel snobby for dressing nicer than other people. I feel like they think badly of me for it, and I don't dress well to make them look bad. On the other hand, when I go to a nice place with the same people, they look underdressed and silly, and suddenly I am the normal one. It's all silly and relative.
All the dress shirts I buy cost $20-30. I never spend more than $15 on a tie. Slacks cost a little more, but you need a lot less of them. The suit I own cost less than $100 new. Of course, you can get all these much cheaper thrift shopping at resale places.
Try to think of it as a lump-sum investment rather than a whole bunch of small, expensive purchases. $600 or so is pretty cheap when you think of the professional benefit it will give you.
Here's my current professional wardrobe:
-Just over 2 weeks rotation of nice oxford shirts of multiple colors
-15 or so ties (way too many... my wife is tie-happy)
-5 pairs of slacks (brown, navy blue, black, grey, black with white stripes)
-a whole bunch of colored socks (guessing 8 pairs black, 4 brown, 3 blue)
-a reversible black/brown belt
Tips:
-make sure socks match the color of your slacks. Don't wear white socks.
-try to avoid drying your nice shirts because they will shrink and look bad. Put them in the dryer for maybe 5 minutes to fluff them and get out wrinkles, and then hang them. I put them on a hanger and stick them on the shower rod since I don't have a clothesline.
-don't wear patterned shirts with solid ties or vice versa
-when you tie a tie, make sure the bottom of your tie touches your belt buckle
Hope that's helpful.