What needs to be repaired with piston eaters? Approximate cost??

Hello !! Have just seen on the internet an offer for a Keeway Matrix. the scooter should cost 180 euros, has no damage to disguise or anything else, was in winter last year still full driving ready, papers are also present. Despite all this he has but now a piston eater. Now I wanted to know what needs to be repaired? what costs that so about ?? Thank you in advance !! LG Rouvus