Holy flippin' mark-up! $65 for four bottles that contains maybe $1-2 worth of chemicals?
Anyways, as someone stated above, these kits test for the presence of MDMA, not necessarily all adulterants. There is the issue of cross-reactivity as well.
It's better than nothing, but I'm not sure I would trust a drug that hadn't been run through an HPLC.
[0]: http://www.dancesafe.org/product/coomplete-adulterant-screen...