you get what you drafted. it should be Besieged, Scars, Scars.
I would recommend checking with the local store ahead of time as some stores will do mixed drafts such as skymoon31 indicated. Other times you will see the draft be all Scars of Mirron, or all Mirrodin Besieged.
Gamer7129 is right in that the standard format of drafting will be 3 packs.
No prize seems like a little bit of a let down though.
15$ with no prize? what a crumby store, just organize with a few of the guys and buy a box (36 packs) and draft on your own. Should cut the price in half , but still no prize.
On second thought...maybe the prize is more metaphysical...as in if you play, you win because you gain knowledge and experience, and in order to have gained said knowledge and experience you must pay the price.
I'd still rather win booster packs.
i got an onslaught draft coming up. we get 6 packs so nvm its sealed i think? anyway its $30 buy in and first place gets 22 packs, which i doubt ill win but for $5 a pack is it worth it?