Why not raffle the prizes to anyone who bought X packs? Why always give to the whales who already have everything? What about the little people, the krills? It's not like you're gonna ruin the economy if a guy who had nothing gets 1 land plot or 1 runi.
I know you want to boost the sales with this, but you could've make it that every X packs bought gets you 1 ticket for the raffle, so whales still get better chance of winning, and krills also get a chance, no matter how small it is.