There are only 2 ways to influence translator cost - pay translators less (the crowdsourcing approach) or make them more efficient. We can have a vastly greater impact on cost by linking the time it takes to complete a translation and improving productivity than focusing on driving down word rates.
There is no one magic bullet. Translators natural rate of translation improves over time as a consequence of a number of factors. Content familiarity, memory reuse, terminology in context search, pre-translation quality improvement, automated spell checking all add incremental improvements.
One of the first factors we tracked was translator quality (via spot checks, reviews, client feedback) and there is no correlation between translator speed and quality. Some of our most productive translators consistently score 5 out of 5 ratings on quality across 500+ jobs.