Cost of dresses?

The material alone for many of these dresses would far exceed $500.

Thelma has addressed this on the show (as well as some of the other business people the Travellers deal with). Clearly everything is expensive but they are very secretive about their spending and disclosing who much someone spends on the dresses would ruin her credibility in the community and cost her business.

No, I wouldn't be surprised if $50,000 or so was more accurate. If you've ever watched Say Yes To The Dress you know that a couple grand is pretty bargain basement for wedding dresses these days. Most of the brides on that show spend much more than that and their dresses are off the rack. Those giant custom made gowns covered in crystals and rhinestones could reach 50 grand or more easily. But of course it's only a very small percentage of travellers that have those big gowns and elaborate ceremonies, just like any culture. Assuming they all do would be like watching Keeping Up With The Kardashians and assuming all non-travellers must live like the Kardashians.