The worst that could happen is he doesnt send it and u wait 3-4 days and get your credits back, but if he does send it, (WHICH I THINK THAT HE WILL) your helping another person build up feedback and a successful Listia account....
It will probably cost $3-$4 to ship and tracking is like $1.50 more... but since im in mass too, if i win, itd be cheaper.. tracking is the best way to keep u safe... bc u dont get credits til winner has the game in hand... as long as u put tracking on it, u and Listia will know when winner received it so u can get credits quick..
FWIW, if you ship first class you get tracking for free, and it only costs 3$ or less (not including the envelope which you can get 2/1$ at dollar stores)
when i sold my old games and shipped them it only cost me ~2.25 + envelope