If they are in perfect cosmetic and working condition (with manufacturer's original box and packaging) then not much really. If they were the AR18s models (in perfect condition) then I would bite the seller's hand off if they were offered for £100. (Put them with a professionally serviced NAD 3020a and have a blast!)
However that sort of condition for 30+ year-old ARs would be miraculous (even with recently - and properly - replaced foam surrounds which is unavoidable even with examples that never left the box.)