Silver costs less than $18/tr.oz on the metal markets. You'd have to process an awful lot of film in order to get $1000 worth out. Sticking wire wool in seems to be pretty effective at detoxifying fix, even if you do only end up with worthless sludge. Whilst it seems a shame to throw silver in the bin, it's actually not that expensive (compare this with Gold which costs over $1k/tr.oz) and requires pretty much industrial-scale recovery to be economically viable.