65,787 alches which = 17,565,129 RSGP in nature runes. Then the price varies from what you choose on alching. 1k alches/per hour so roughly 66 hours. And then the price the person takes depends on 66 hours of labour. You could just auto click at soul wars and get no randoms.
Edit: loss won't be 17,565,129 it will be much less if you alch an item that is profitable or barely any loss.