Document review in e-discovery is costly. Contract lawyers are less expensive than associates. Going offshore can lower costs yet more. 

I await published case studies detailing offshore document reviews. In the mean time, several offshore companies or US companies with offshore operations now offer discovery document review services. Here is what vendors say on their websites:

Aphelion (formerly BPL Services): “Aphelion’s management team has been involved with substantial document review projects in litigation matters handled by the firms DLA Piper Rudnick Gray Cary and Womble Carlyle.”
ITELS: ” ITELS document review team includes top-tier US and Indian lawyers experienced as litigators and corporate attorneys for international and domestic corporations…. Review of documents in complex matters and corporate due diligence… Review for relevancy, privilege, and issue coding.”
Lumen Legal: “Lumen Legal dramatically lowers the cost of document review typically associated with major litigation…. as a pivotal provider delivering the right mix of on-shore and offshore talent, we can provide 24/7 workflow at cost savings of 50% or more over traditional models.”
Pangea3: “Analyze documents for materiality, privilege, and responsiveness to discovery requests, subpoenas, informal and formal regulatory requests… Conduct large-scale electronic file reviews.”
QuisLex“Our highly trained and specialized litigation support team works closely with your legal team and performs the following services… Subjective coding (creating substantively coded indexes etc)… Relevance and privilege analysis”. (See also SQ Global Solutions.)
Tusker Group: “Tusker Group has the ability to align domestic and international attorneys to provide high-quality, cost-effective first level document review: relevancy, privilege, confidentiality, issue content and responsiveness.”

I have included in the above list only those vendors whose web site clearly indicate that they perform document review in litigation. Other vendors may also do so (see the list of outsourced legal services).