I am looking for a website with discounted Tom Arma costumes or similar high quality infant costumes. Any ideas? Thanks!

Ebay is the only place I have seen them, but many are New With Tags (NWT)
I believe Babystyle in the Atrium Mall in Boston carried many Tom Arma Costumes. They recently went out of business at the Mall and I have seen many costumes come up on ebay as a result so like I said, many are brand new.

I bought my son a nwt one on Ebay a couple of years ago. They had a ton then. It was very reasonable and oh so adorable.

Thes best thing that I have found is to google "arma craigslist" and lots of craigslist postings come up from all over the country- must quicker than looking through individual areas. Try contacting the person and seeing if they are willing to ship. You have to put trust in the person to ship after you have sent the money though because it is not like ebay- there are no real "rules" to shipping, etc. Good luck!