I agree they may well have been looking at the figures but it may well have been their intention to have always ditched it once the contract to ESPN ended.
Fairly sure the Top14 rights were not to do with ESPN. Top 14 was on Premier Sports 2012/13 and BT this season (2013/14) and BT owned the rights those 2 seasons but subcontracted them to Premier Sports 2012/13 as BT's own channels were not launched until Aug 1st 2013.
Could it be that Top 14 is less of interest to BT as they have added the top choice English club picks from next year for the European club competetition? There's a good chance that both Sky and BT put in offers but Sky's looked better to the Ligue Nationale de Rugby! Sky also patching over some losses (AP, new EC) with P12 and T14.
Main point though is that any T14 contract with ESPN UK ended 2011/12.