Exchange guns for gift cards!!

In San Francisco, the police did a campaign to have less guns in society.Participants received $100 gift cards or shot guns, $150 cards for revolvers or automatic pitols and $200 cards for assault-typeweapons. I think this is a good idea. But I also heard a sad news that in the U.S., you can buy junk guns for about $10 and some people buy these to exchange with gift cards and buy a better gun with those cards. What would you do if you live in America? I hope less people will cheat .