I'd say a combination of the third option with slightly less wording, and perhaps a slightly more believable price. Because to be honest, $50/month would have people calling bullchocolate. If the "real" price was $25, it'd be slightly more reasonable.

The "Opening Sale" tagline would get a few people, I'd wager, and you'd be able to run the deal for a little longer to let word get out - perhaps mentioning that it's for three days only before the service starts?