All those providers look pretty dodgy. No contact details and only accept payment in bitcoin.
For example, with overseas pharmacies located outside of the US and selling generic drugs at much reduced prices, the pharmaceutical industry (via their organization LegitScript) work hand in hand with the VISA organization to take away credit card facilities from these overseas pharmacies, making it harder for them to do business.
In this paper on PubMed, the author states that it is unethical for the FDA to regulate helminths and bacteriotherapy.
Looking at the list of helminth providers on helminthictherapywiki.org, it seems that www.wormswell.com are a very well priced service, charging just $85 for a single dose of 5 Necator americanus larvae. Unfortunately Wormswell cannot ship to the US (it says so here).
And biomerestoration.com look even cheaper, charging just £15 for 5 helminths — but they sell Hymenolepis diminuta cysticercoids helminths, rather than Necator americanus.
Whereas most of the other providers are charging in the order of $2000 or $3000 for a two or three years supply of helminths. If you only want to try one small helminth dose to see if it helps, you wouldn't want to pay $2000 for a two or three year contract.