I agree with logan.
the latest TINSA report states that for the islands the sqm comes out at 1672 euros.
So a property of 345sqm would value at 576840 euros
of course there is a very large plot of land as well (15,484 sqm), so that should help the valuation.
But is it is a ‘country’ villa, ie a finca, so the banks would only give a 50% mortgage in 99% of cases and the sqm would not value like urban plot/builds.
furthermore from the photos there is no way that property is 345sqm unless the basement equals or is close to the size of the ground floor. And you cannot give the basement the same value per sqm as the above ground floors.
My opinion only though
EDIT: I don’t know the islands that well. maybe this property is in a very exclusive area that helps bump up the price?