The Tsavo man-eaters were not measured as a pair in pounds in the usual historical sources. What’s commonly cited is that one of the lions weighed about 857 pounds (389 kg), based on a later account referenced in public discussions of the Tsavo lions.

If you meant the weight of the famous Tsavo lion specimen , that figure is the one most often repeated. If you meant the two lions together , the sources I found don’t give a single combined pound total.