Lucaille has some good Gumi wigs for under $15, iirc, but shipping is expensive. However, if you do a batch/bulk taobao order, the (price+shipping)/wig doesn't come out very bad.
Lucaille ships overseas themselves, but they don't get an EMS discount the way taobao shopping services do. Fantasy Sheep is another that ships and doesn't get an EMS discount. Note that FS wigs tend to be darker than their studio-lit photos. If you choose either of those sellers, make sure to link to their taobao product link, as they are much less expensive than the ebay product links.
I don't really know about anything Stateside, tbh.
Oh, and I have so far personally used Classe (high-quality Japanese wig merchant), Fantasy Sheep (taobao), and You-to (taobao). I have real life friends who have used Lucaille (taobao), Meilifang (quality taobao) and Airily (another quality Japanese wig merchant). However, quality Japanese wig stores are much more expensive, and Classe discontinued their styled chara-wigs because of recent trademark enforcement going on in Japan.