(The Business Insider) The writing was on the wall from the beginning. When Virtu Financial — which had grown to become one of the largest high-speed trading firms in less than a decade — acquired rival KCG in July, there was an understanding that costs and staff were going to be cut fast. Virtu had spent $1.4 billion on its purchase and was already known for a lean business model. Virtu had just 150 staff, compared with 1,100 at KCG. That’s to say nothing of KCG’s old-fashioned flash with cash reputation…..