Disagree.
Sigurdsson was by some distance Swansea's most important player - he was directly involved in something like 50% of Swansea's goals the season before. They were always doomed for relegation when he left - it's why he was so important for them/commanded the fee he did.
We paid what he was worth to them - they'd have kept him too, if he didn't go on strike.
I often joked on here that if we take away Sigurdsson's goals/assists and their points, we'd be in a relegation fight. Not long after he went, we were...