You can of course also just take a cheap flight to Mexico for that amount and buy an abundance of real peso coins in the many coin shops they have around... Really, I think I've completed almost a whole type set of Mexican peso circulation coins there (1905-today) for less than $100, including almost all silver, excluding all gold. Only a few key coins (1 and 2 cent 1915, for example) are still missing.
Especially Mexico City is a great place for bargain hunting (also for
US coins).
@silverwolf: I'm not sure about that, as the ad clearly reads that they're reproductions and silver plated. So the seller isn't trying to fool anyone, imho.
@justinokay: true, Mexico issued a lot of .100 and .300 silver in the past. There's still so many around that you should be able to get them at silver value or less over there.